INC. The idea would therefore be perform the interpolation on a log scale already by transforming the data to its logarithm first and then perform the interpolation. Using the TREND Function 4. Value 'Get. Next, select the cell where you want the interpolated value to appear and use the formula =FORECAST (x, known_y's, known_x's) to calculate the interpolated value. The trilinear equation is derived by applying the linear interpolation seven times (see Fig. For example, for WS[0] which is 6. You just need to insert the formula. e. Locate where 12 bar a (A) would be. ‘time’: Works on daily and higher resolution data to interpolate given length of interval. 3%, you can just interpolate those two points. For example, if you're using data about how sales increased as a company hired more sales professionals, the numbers of sales professionals go in column A, and the corresponding total sales go in column B. That said: for the example in the sample set I chose a 3rd order polynomial to "match" the spline look and it found an. Anyways, to interpolate for 219. This help content & information General Help Center experience. Linear interpolation, also called simply interpolation or “lerping,” is the ability to deduce a value between two values explicitly stated in a table or on a line graph. interp(). 2) Calculate slope and intercept for each pair of points (for each firm) as part of the lookup table. Step 4: Create 3D Interpolation Graph. Select the range of 12 data points for the X Function Argument field. Value = 0 Then RowToTop = Row - 1 Do While RowToTop > 0 If Cells. CountIf (rng, typeName) 'Set the Row up on the. In Mathcad. But as long as the known-Y and known-X arrays have just two elements each, FORECAST interpolates the actual data points. INTERPXY automatically. Remember that likely none of us on this side of the internet has done this sort of calculation. Interpolation (scipy. EPL_table_Pol = EPL_table. richthorpe, this post is unlikely to be very useful for your purposes, but you may get some interest from it. I have found fomrulas for vlookup and xlookup but not for hlookup. The linear interpolation equation above can be implemented directly in Microsoft Excel provided the tabulated values are monotonic in x, that is the x-values are sorted and no two are equal. 1, (p. Given two known values (x1, y1) and (x2, y2), we can estimate the y-value for some point x by using the following formula: y = y1 + (x-x1) (y2-y1)/ (x2-x1) To create a sample linear interpolation formula, follow these steps: Type the following values in a worksheet: excel Copy A1: 9 B1: = (A7-A1)/ (ROW(A7)-ROW(A1)) A2: =A1+$B$1 A3: A4: A5: A6: A7: 11 Select cells A2:A6. c. Interpolation can be used to estimate the thermal resistance for non-tabulated values between the tabulated ones. The approaches discussed here are suitable for hand calculation when you have limited tables available, but if you're implementing a computer routine to produce p-values, there are much better approaches. 96 at a speed of 1000 should be 54. Save as . I'm trying to get the interpolated Cl and Cd from this table. and A2 has the value 2, B1 has the value 5 etc. Method 3: Interpolate in Graph Using SLOPE and INTERCEPT Functions. But for small portions of the table (for example between rows 1 and 2, 2 and 3, 3 and 4. The completed table should look like this: Bilinear Interpolation in Excel. Given an X vector, this function interpolates a vector Y based on the input curve (XY Range). V contains the corresponding function values at each sample point. #10. For example, look up the price of an automotive part by the part number, or find an employee name based on their employee ID. For sure, B1 will be 1, and B32 will be 32, but B2:B31 should be interpolated from the A1:A6 table. 1. 005629 Hint: define the vectors for the known values, T, P, and T_i (the temperature that. Public Function InvBilinearInterpolation (xRange As Range, yrange As Range, zRange As Range, xyCoord As Double, xyPick As String, zCoord As Double) As Double ' This is a reverse bilinear interpolation. Use of Linear Trend Method. 5 psia "thermo" wrote: I was surprised that Excel doesn't have a built in linear interpolation routine. 2- no interpolation, the upper bound/ last value. Learn how to estimate data points within an existing data set using simple mathematics, the FORECAST function, or a third-party add-in. 32 9M 0. Step 1: Firstly, identify the independent and dependent variables for the function. First, the value of x will go, then add the y-axis values and finally add x-axis values in the formula and click Enter. 4 0. Using linear interpolation, estimate the. two dimensional lookup with interpolation. Range ("A2:A" & lastRow2) For s1Row = 2 To lastRow1 typeName = Sheets (SourceSheet1). Build an interpolation program to interpolate any of the given properties from a specific table of data for any given temperature. This seems really common. For instance, for x=3 with your example lists, the containing interval would be [x1,x2]= [2. Different methods of interpolation include linear, quadratic, and spline interpolation. The transpose was necessary with matrix logic to accommodate a table (starting at xQuad and then yQuad) of possibly linear-interpolation adjusted outer influence points created by IF logic, with 4 XY points defined in 8 columns shortly after each inner interval as defined by the original XY data columns in A & B. The file here is an excel file and I have imported them into matlab and named the variable naca which is the size of 395*4. i. At the begining I needed the function to do interpolation only but when I started to get X and Y values outside the ranges appearing in the table, I think the macro needs to be modified. 1 or >0. the hours of daylight for the 15th day of each month in the year 2006 in San Diego, California. Applying the FORECAST Function to Do Linear Interpolation. But as long as the known-Y and known-X arrays have just two elements each, FORECAST interpolates the actual data points. mmm "you want to build a conditional linear interpolation" and said "Say ID is AED" let me speculate what you really want, First you have a Function (that do linear interpolate) Second you have (for easy explain) a table that have 3 columns: Column 1: ID (value that identify which ranges will use) Column 2: Number of values have varibale X. Here is an Example for a mathematical solution: Generate x-values x (we need them as array for the next 2 steps) Calculate the slope m for the given row values. You want to obtain the value (by linear interpolation) for height of 7 and distance of 20. Applying the FORECAST Function to Do Linear Interpolation 3. a. 2 0. I understand table format is good rather than a list format but what I mentioned is just an example, in actual the data could be much much bigger (usually in my case it reaches 500-600). Below is code that. The mathematical equation for this case is as follows: y= y 1 + (x-x 1 )⨯ (y 2 -y 1 )/ (x 2 -x 1) We need the value of y corresponding to x, which makes point B (x,y). I am trying to obtain an estimate of an x and y value given a z value using a x,y,z matrix. 4 to find the resultant. In this case, the values in cells D3 and D6 are missing. Best. values between two tabulated points) in steam tablesThe solution required would be a dynamic solution that will interpolate data in each and every blank sequence, irrespective of the number of blanks. Once we click OK, Excel automatically fills in the missing values by adding 3 to the each. Post a small Excel sheet (not a picture) showing realistic & representative sample data WITHOUT confidential information (10-20 rows, not thousands. Your screen must be similar to this screenshot. 4 you should just be able to use lookup to get the values for 219 and 220 (I'll call them 3 and 4 for example) and then take a weighted average: 3 + (4-3)* ( (219. Table of Contents hide. 2. Count If nR < 2 Then Exit Function If x < rX (1) Then ' x < xmin, extrapolate l1. Select your data > Data > Insert > Table (Click the checkbox the My Table has headers. This isn't the greatest example since the values above and below for each LD value remain. With Excel it’s a little more complicated; you can use the FORECAST. I need to interpolate between the values, ie A = 11 and B = 1. =B2+ (A4-A2)* (B3-B2)/ (A3-A2) In the above example, the formula’s last section, highlighted in red, calculates how much time taken changes whenever the speed of the bike changes by 1. We can use the following basic syntax to perform linear interpolation. Open the "Data" tab and click "Forecast Sheet" in the "Forecast" group. Solution: The procedure you use to solve this problem is essentially an extension of the method used for the single control parameter table. Three options appear in the select a function box, i. 5 (in addition to 0. 4 Torque. 2. In another table, I get a calculated elevation and then I would like to use Excel (VLOOKUP or some other function?) to look up the corresponding area for that elevation in the first table - but be able to linearly interpolate between elevation values to get the corresponding. 3. Table of Contents hide. Step 2. I want to interpolate for a given x1 value between the y values using the hllokup function also. In one column of an Excel sheet I have an ascending series of integer values, which increment after several rows. . The INDEX function can find data in a 2d table if we use both the row_num and column_num arguments. Usually labeled Saturation Temperature and Saturation Pressure. 5/19/10 4:47 PM. Syntax and Parameters: Pandas. Interpolation is a mathematical or statistical tool that predicts the values. If the r0 value falls between two values a function needs to interpolate and get the value for that specific r0 value. The results always pass through the original sampling of the function. The data shows that we have got the temperature details of the Bangalore region for some date. Summary. See an example of linear interpolation with a table of data and a formula. Vq = interp2(X,Y,V,Xq,Yq) returns interpolated values of a function of two variables at specific query points using linear interpolation. In mathematics, linear interpolation is a method of curve fitting using linear polynomials to construct new data points within the range of a discrete set of known data points. I know how to get value that is in "cell" of that table using. The first step to performing linear interpolation with this method is to create a chart with all of your data to optimize your organization and ensure accuracy in your calculation. To start, place at least two columns of data in an empty Excel worksheet. Do Interpolation of Non-Linear 2D Data in Excel. Made by faculty at the. Linear Interpolation in Excel: Step-by-Step Example Interpolation is the process of estimating an unknown value of a function between two known values. Step 3: Utilize Excel VBA Code to Build a User-Defined Function. here's a possible mathematical solution: Rather than working with the raw data x and y, instead try plotting x and a^y, where a is the base. How to Multiply Column by a Constant in Excel. vq = interp1 (x,v,xq) returns interpolated values of a 1-D function at specific query points using linear interpolation. . Choose the Scatter chart type and select the scatterplot. For the "Value III" I know the math formula when you interpolate r numbers between two numbers a and b then the distance d between interpolated numbers is: d = (b-a)/ (r+1) And the values of those interpolated numbers are: r1 = a + d r2 = r1 + d or r2 = a + 2*d r3 = r2 + d or r3 = a + 3*d. This is the easiest way to interpolation by set up formula only 1 time and we can use this forever. Addendum: Advanced Solve Functionality Setup in Excel 2007 Advanced solve functionality is available in Excel, it just needs to be enabled through an Add-In. The code to interpolate is basically a one-liner, from scipy. To set the scene, I have 8 calculated columns which use the 'long code' (to avoid having 40 columns) to find an interpolated value from one of a few lookup tables. Thus we can find the probability for 1. The corresponding desired pressure is then in the next column; in this case, 7. Excel interpolation with results in situ. . Since your unknown x value is the year 2001, you will use the values in the table for 2000 and 2002. Before we can start our bilinear interpolation in Excel, we’ll need. Below are the steps for using linear interpolation: 1. LINEAR Interpolate function from the list of suggestions shown by Excel. 2. Copy/paste the formula into other cells with missing values, (provided that you don't have 2 missing values in a row). excel & macro excel & vba interpolation table work Replies: 3; Forum: Excel Questions; V. Option Explicit Public Sub LinearFit () Dim rx As Range, ry As Range Dim x () As Variant, y () As Variant Dim i As Integer, j As Integer, N As Integer, M As Integer M = 6 'Columns N = 44 'Rows Set rx = Range ("A2"). Hello all, I just wanted to stop by and share my work. use this with index and index +1 to find to two values around your input. If match_type = 1 (default value if omitted), Excel returns the greatest value less than or equal to the lookup_value. This is OK for vertical lookups, but does anyone know a simpler way to interpolate results in a two-dimensional matrix? This thread is. In our example, the time taken changes by 1 minute when the speed of the bike. The FORECAST function, which can be used in Excel to perform linear interpolation, is =FORECAST (x,known_ys,known_xs). VBA doesn’t recognize these functions by themselves. Here’s a description of what you need to know about each of these arguments: Argument. a present or future value table. 3 in Torque. 384 kPa. Define a set of y values. For linear interpolation have the sheet active and run the following. Step 3: Prepare Dataset According to X and Y value. With XLOOKUP, you can look in one column for a search term and return a result from the same row in another column, regardless of which side the return. . Step 1: Firstly, identify the independent and dependent variables for the function. My final data sets will consist of a couple hundred sets of data with each set containing 35-55 data points needing to be normalized to. xll. I will assume linear change between each value. This equation will help you for interpolation. . g. This functionality is similar to that of the Simulink ® and Simscape™ Lookup Table blocks. Method 1: Mathematical Equation for Linear Interpolation. Sure. 4 to find the resultant. In MATLAB, you should use the function interp1. You can now use the “Transpose” option found under the Chipboard option in the “Home” ribbon > Paste Option. g. I will discuss these in future articles. If you have an old release of Interpolation. For example, say for -173. 31 6M 0. I have also tried interp1 function to interpolate. Xq and Yq contain the. I see that this a reply on this post (Interpolate on log scale) provides a nice way of interpolating along the y-axis; i. Excel Q. Step 3: Interpret the Polynomial Curve. (a) Trendline for Data Extrapolation in a GraphIn this video I will share with you a VBA code to automatically fill out a X and Y table based on partial data and the interpolate logic. Every time you change one of the referenced values the calculation will be run again. Hello everyone! I'm a fairly basic user in excel so I'm looking for some help. 96 and speed 800 result in 50. =iferror(forecast. Use GRIDXYZ to map set of scattered (x,y,z) data points onto a uniform rectilinear grid. I have also tried interp1 function to interpolate. 96 and speed 800 result in 50. You can use them to perform simple table lookup, as well as, interpolation and extrapolation from tables with one, two or three independent variables. Click the insert function button (fx) under the formula toolbar; the dialog box will appear, type the keyword “PERCENTILE” in the search for a function box, and the PERCENTILE function will appear in the Select a function box. Step 1: Finding the Value of Z. This data should contain two columns: one for the independent variable (e. The =INDEX and =MATCH pick out the relevant two points on known_y's and known_x's. Time series B has more data points, at irregular intervals, over a shorter time span. xls, since then it will not be available to other users of the spreadsheet. This video demonstrates how to use ExceLab Add-in INTERPXYZ() function to interpolate scattered (x,y,z) points onto a uniform grid and plot the data with Exc. 2) Type =FORECAST ( in the selected cell. Is there a formula to automatically do this? My current code is below and it's a bit clunky, especially trying to apply the formula for hundreds of row of data. My problem is this: I have some data from a geophysics survey in a simple xlsx sheet (Excel 2010). interpolate (which is fantastic!). For instance if I look up 130, and my table has values in column 1 of 100 and 200 (in the first and second rows). 96 at a speed of 1000 should be 54. Linear interpolation, also called simply interpolation or “lerping,” is the ability to deduce a value between two values explicitly stated in a table or on a line graph. 4-219)/ (220-219)) Of course, the values would be references, with 3 and 4 being received from lookup function. -- MechEng2005. Use the linterp function to perform linear interpolation. XonGrid Interpolation Add-in (sourceforge. I would like to ask you for help on interpolation of the values for 3D chart. Use INTERPXY to map a. 2 AOA, I want to find out the corresponding Cl & Cd. If not specified, x is taken to be the indices of y ( 1:length (y) ). It is considered to be the simplest of all methods to interpolate between two values when values are approximately linear. In Python, Interpolation is a technique mostly used to impute missing values in the data frame or series while preprocessing data. Linear interpolation. Step 3Vq = interp3(X,Y,Z,V,Xq,Yq,Zq) returns interpolated values of a function of three variables at specific query points using linear interpolation. An Interpolation function () is defined by a table or file containing the values of the function in discrete points. Map a set of scattered (x,y) data points onto a uniform grid for curve plotting. With optional arguments, you can control the interpolating spline properties. So I have a very large set of data (4 million rows+) with journey times between two location nodes for two separate years (2015 and 2024). If I assume that it must be done in Excel. Excel's solver tool is a really powerful way to perform nonlinear interpolation. In conditional formatting options, selects color scales. Naturally, multivariate interpolation gets more complex than simple single variable interpolation. If y is a matrix or an N-dimensional array, the interpolation is performed on each column of y . if the value to look up is in A1, the range of data a2:A10 and the data sorted ascending. Jun 12, 2013. The first way is plugging in the basic mathematical formula for linear interpolation. You have to use it as native function of Google Sheet 1. Yes I would like a cubic or quintic spline interpolation. i hope this clarifies This message was edited by c_t on 2002-09-06 04:33 This message was edited by c_t on 2002-09-06 04:35 ★ Want to automate Excel? Check out our training academy ★ Download the example file★ Torque for a temperature of 29. Time Series in Excel 2003. It can be used to map a set of scattered data points onto a uniform rectilinear grid for the purpose of plotting a 3D surface in Excel. 3 Torque. Performing linear interpolation in Excel is quick and straightforward. Follow the steps given below to do it on your own dataset. Type the function related to the interpolation that you wish to solve. Each cell in B1:B32, should have the corresponding value from the curve of the original data. Before we begin we will need a group of data to interpolate missing values in Excel. The linear interpolation equation above can be implemented directly in Microsoft Excel provided the tabulated values are. The following Microsoft Excel formula performs linear interpolation by calculating the interpolation step value:. Converting Data to a Table. 1. This answer is in two main parts: firstly, using linear interpolation, and secondly, using transformations for more accurate interpolation. ” Choose the cell where you wish the data to be pasted. If we leave the Type as Linear, Excel will use the following formula to determine what step value to use to fill in the missing data: Step = (End – Start) / (#Missing obs + 1) For this example, it determines the step value to be: (35-20) / (4+1) = 3. In this method, we will use a VBA code for searching a value in a range, and then, get the desired result with the help of the interpolation. In Excel, we use a FORECAST function and a LOOKUP function to do a linear interpolation. Suppose that one has a table listing the population of some country in 1970, 1980, 1990 and 2000, and that one wanted to estimate the population in 1994. 4); three times each to determine the points p1 and p0 as illustrated in the 2D bilinear interpolation, then one more time to compute the point p. 5, create a formula below it that just adds 1, and fill this down as needed. 1. o From Excel, do Alt F11 to open the Visual Basic Editor. Extrapolation Formula. 4) Solve y=mx+b to interpolate. Here is how to do it. To interpolate linearly in Excel, follow these steps: Enter your data into an Excel worksheet. Polynomial Interpolation in Excel: Step-by-Step Procedures. I don't want to restrict myself to the two blank sequences in the test data by manually doing it each for each sequence. Both Kenneth's and Cringe's solutions assume the relationship is linear (which it is in the table, but not in general). That is because I do not know how to use the Excel table structure references to: a) get only the first row. b. Examples. 4-219)/ (220-219)) Of course, the values would be references, with 3 and 4 being received from lookup function. 544 at 1. For Non-Integer Month number, I need use some kind of "linear interpolation" approach to get an approximate LMS data. Yes bilinear interpolation would be the best approach for this approximation. Once you get the shape of a sorted out you can just do. If you are fond of VBA and want to do VLOOKUP and Interpolate in Excel using VBA, then this method will be a handy one for you. I need to perform a 2-way lookup on a table. The resulting scatter chart will plot the result of our cubic spline interpolation. =B2+ (A4-A2)* (B3-B2)/ (A3-A2) In the above example, the formula’s last section, highlighted in red, calculates how much time taken changes whenever the speed of the bike changes by 1. You will find attached an excel file with the problem presented here. 5. Use INTERPXY to interpolate from a set of (x,y) data points at an arbitrary point. 2. How to Calculate the Area of a Parallelogram in Excel. Temperature 39. In such cases, interpolation is required to obtain the correct value. Fixing my interpolation function. การใช้ excel ในบทความนี้จะนำเสนอการใช้ excel ช่วยประมาณค่าในช่วงข้อมูล โดยวิธีการประมาณค่าในช่วงแบบเชิงเส้น (Linear Interpolation) เป็นวิธีที่ได้รับความนิยม. , I have a table with different cases from A3 to S3 and an m value ranging from 0. 2d interpolation table (Matlab) 0. select (B1:B3,B3:B6,B1:B9) then editfillseriestrendOK Another method is to set each blank cell equal to the. First, organize your data into two columns with known values. V contains the corresponding function values at each sample point. This uses Excel Forecast function =FORECAST (x,known_y's,known_x's). Method 2: Interpolate in Excel Graph Using Trendline. Is there anyway I can get Excel to interpolate the. Syntax PERCENTILE. Interpolate in Excel Graph: 6 Ways. If it cannot interpolate for the k. How does Excel interpolate / imputate missing values in time-series. You can use the linear method if your data set creates a straight line and a calculator or software if the data set creates a more complex shape. Use the # of days or the date as the X value and the value for the Y value. Learn how to use the FORECAST function and XLOOKUP to perform linear interpolation in Excel when there are only two or more pairs of x- and y-values. 6% and 520 were the results achieved, I need to figure out what the weighted average is between 11% and 12% whilst at the same time the weighted average between 500 and 550 to arrive at a final exact figure. It calculates the dependent variable (Y) for a given independent variable (X) by fitting a straight line to the available data. Converting Data to a Table. The set example is this, as shown in figure 1. Type. And our initial data set would look like this: Firstly, we can simply input the basic mathematical formula of linear interpolation in Excel to get the result. 3. g. . INC will interpolate when the value for the specified percentile is between two values in the array. This could be in two directions:. We want to reconstruct a polynomial that attains the same function values as f. ‘index’, ‘values’: use the actual numerical values of the index. You can use Excel to project values that are based on existing data or to automatically generate values based on linear or growth trend calculations. See below figure. When the lookup is intermediate of two values in the lookup column, it returns the lesser value from the second column. Select the range A1:B13 shown above. Re: Interpolate An Array Of Numbers. Linear Interpolation. Also, it calculates (or approximates) the. The table will be placed in sheet 3 of the Excel Spreadsheet. Vector xq contains the coordinates of the query points. I have a specific point of temperature and pressure and need the thermal conductivity interpolated from them. Clear searchBasically, the Excel formula is simple: =_X1+ (_X2 – _X1)* (Y – _Y1)/ (_Y2 – _Y1) Linear Interpolation [/captionThis formula can be written in a more familiar style, the relationship between the known. Thread starter Pigankle; Start date Dec 15, 2011; Tags interpolation lookup P. It allows you to do linear or spline interpolation for a general curve in n-dimensions. 2. VLOOKUP then returns the first name for id 601, which is Adrian. Temperature 29. Open your spreadsheet and enter your data. Sheet1. 1 Answer. For example, look up the price of an automotive part by the part number, or find an employee name based on their employee ID. Since we’ve grouped the table into cells, we can pass the column [Table Data]. There are functions to create that table very easy. I'm trying to get the interpolated Cl and Cd from this table. 6084x + 30. Sorted by: 8. 1. Add input cells for height and span in J1 and J2 respectively. Unable to download your file. I am able to do bi-linear interpolation if I know the x and y values to obtain a z value but I am not sure how to do the reverse process. For this to work properly, the values in the lookup_array must be in ascending order. For example, if 11. 0915. interpolate is a convenient method to create a function based on fixed data points, which can be evaluated anywhere within the domain defined by the given data using linear interpolation. I'm guessing I'd also need to make the code do linear interpolation between the table values in that case. I'm trying to construct a workbook with the ability to interpolate between 2 values. Therefore, x = 2001, x1 = 2000, y1 = 100, x2 = 2002, and y2 = 90. ‘time’: Works on daily and higher resolution data to interpolate given length of interval. 1) a lookup function to locate the interval containing new_x (I tend to use the MATCH () function). got me sir?)We would like to show you a description here but the site won’t allow us. I needed to interpolate data from a table to calculate the internal energy at a given pressure. For sure, B1 will. xla (with new functions) In this page you can download an Excel Add-in useful to linear, quadratic and cubical interpolation and extrapolation. 4 Torque. Indeed, we will establish analogous formulas for completely gen-eral function interpolation based on the same matrix factorization method, resulting in a general divided difference calculus for univariate interpolation theory. 4 MPa and T = 72 P oC, the enthalpy can be estimated by interpolation using the rows from Table A. Excel formula : Interpolate in a second column between dynamic repeating integer values in the first column. Replace "x" with the value you want to. Verma @ 1 person found this reply helpful. . For example, say for -173. 2 0. I have attached. Setting upper and lower limit for an Excel histogram. I have a table that shows me a chemical concentration value based on temperature, pH and ammonia. Re: A Formula To Lookup And Interpolate. Failing to follow. Read tutorial and download example Excel file here:do I have MATLAB read an Excel file, interpolate between table values, and then assign the values to variables? Follow 21 views (last 30 days). For x1 and y1, use the input and output from the lower value, and for x2 and y2, use the input and output from the higher value. If one of the looked-up values is not in the exact range, provide the results as follows: 1- no interpolation, the lower bound/first value. 2) Type =FORECAST ( in the selected cell. Select or type the argument as requested by the function [Example: F6,C5:C11, etc. I am trying to figure out a way to interpolate data from a table to calculate a value. 5,3. if the result is not match he will interpolate the result int GUI. If I understand your problem and assuming that the difference. 5 to 1 along A5 to A15. When the data is not linear, the first thing we have to do is to find out the function's behavior. Step 1: Set up Data Model for Cubic Spline Interpolation. See examples, formulas, and download a supporting file for this post. It is only tested on positive values and ten rows, so you will definitely need to adapt it to many corner cases - but it should point you in the right direction: Sub Interpolate () Dim valueToTop As Integer For Row = 1 To 10 valueToTop = -1 valueToBottom = -1 If Cells (Row, 1). 1. If we leave the Type as Linear, Excel will use the following formula to determine what step value to use to fill in the missing data: Step = (End – Start) / (#Missing obs + 1) For this example, it determines the. LINEAR (x, known_y's, known_x's) to calculate the interpolated value. 674), for 40 C in the first column. [Alternatively, type =F or =FORE and double-click the FORECAST. How to Multiply Column by a Percentage in Excel.