In this article, we will show how to do 2D interpolation in Excel. It is possible to do the task of interpolation for both linear and non-linear datasets. You can easily interpolate in Excel if you properly follow the steps. The steps are quite simple. So, without any delay, let’s start the discussion.
2D Interpolation in Excel: 2 Suitable Ways
We can easily do 2D interpolation in Excel. There can be 2 types of interpolation. We can interpolate for linear data and also for non-linear data. Here, we will show you how to do 2D interpolation for both linear and non-linear methods.
1. Perform Interpolation of Linear 2D Data in Excel
It is easy to perform interpolation of linear 2D data in Excel. We will show you 5 ways. Each method is quite easy. You can follow any process to do the task. To demonstrate the methods we will use the following dataset. In the dataset, there is information on the weekly sales of a shop. Here, sales records are for odd weeks. By interpolation, you can find sales of any even weeks. We will find an in-between sales value for week 8. Let’s follow the steps below to learn these methods.
1.1 Apply Mathematical Equation for Linear Interpolation
There is an established mathematical equation for linear equations.
y= y1 + (x-x1)⨯(y2-y1)/(x2-x1)
Using this mathematical equation, we can easily interpolate linear data. So, follow the steps below to learn the method.
STEPS:
- Firstly, find out the coefficients of this equation.
- So, place the values of x1, x2, y1, y2, and x in the Excel Sheet.
- Then, write down the following formula in the F12 cell:
=F7+(F11-F5)*(F8-F7)/(F6-F5)
- Then, press Enter to observe the interpolated result.
1.2 Interpolate Using Trendline in Excel
The trendline is one of the easiest methods for interpolating a linear equation. From the trendline, we can plot a linear line. And from this line, we can interpolate data.
STEPS:
- Firstly, we have to insert a plot from the dataset.
- To do so, click on the Insert tab.
- After that, click on the drop-down menu of the Insert Scatter (X, Y) or Bubble Chart from the Charts group.
- Instantly, a wizard will come out.
- From the wizard, select the Scatter chart.
- As a result, the following chart is shown on the Excel Sheet.
- In the following step, we will insert Trendline.
- To do so, click on the chart.
- Therefore, you can see a plus (+) icon.
- So, click on this icon and give a tick on the Trendline.
- As a result, a trendline can be seen on the chart.
- Now, double-click on the trendline.
- Instantly, the Format Trendline window will appear on the right side of the Excel Sheet.
- Then, give a tick on Display Equation on chart.
- After that, look at the chart and you can see a floating equation.
- So, you can find the value of y from this equation.
- Now, according to the equation, write down the following formula in the F6 cell:
=93.631*F5+7.2024
- Then, press Enter to observe the interpolated result of sales.
1.3 Interpolate 2D Data Using SLOPE and INTERCEPT Functions
We can also build up a formula using the Slope function and the Intercept function.
There is an established mathematical equation for linear equations.
y= mx+c
Using this equation, we will interpolate the 2D data.
STEPS:
- Here, we need to find out the co-efficient of m and c for interpolation.
- Now, write down the following formula in the F6 cell:
=SLOPE(C5:C12,B5:B12)*F5+INTERCEPT(C5:C12,B5:B12)
- Then, press Enter to observe the interpolated result.
1.4 Insert FORECAST Function for Interpolation
Interpolation is one kind of forecasting as we are predicting or anticipating the value. We don’t exactly know the real value exists. So, Excel’s in-built the FORECAST Function comes in quite handy in this regard.
STEPS:
- Now, write down the following formula in the F6 cell:
=FORECAST(F5,C5:C12,B5:B12)
- Then, press Enter to observe the interpolated result.
1.5 Interpolation of 2D Data Using TREND Function
Using the TREND Function, it is quite simple to interpolate from the linear data.
STEPS:
- Now, write down the following formula in the F6 cell:
=TREND(C5:C12,B5:B12,F5,1)
- Then, press Enter to observe the interpolated result.
2. Do Interpolation of Non-Linear 2D Data in Excel
It is easy to perform interpolation of non-linear 2D data in Excel. We will show you 2 ways. Each method is quite easy. You just need to insert the formula. Here, you can follow any method to do the task. To demonstrate the methods we will use the following dataset. In the dataset, there is information on the weekly sales of a shop. Here, sales records are for odd weeks. By interpolation, you can find sales of any even weeks. We will find an in-between sales value for week 8. Let’s follow the steps below to learn these methods.
2.1 Interpolation in 2D Using GROWTH Function
Excel has another built-in function called GROWTH. The GROWTH function is more reliable and accurate for exponential and non-linear datasets.
STEPS:
- Now, write down the following formula in the F6 cell:
=GROWTH(C5:C12,B5:B12,F5,2)
- Then, press Enter to observe the interpolated result.
2.2 Combine FORECAST, INDEX, and MATCH Functions for Non-Linear Interpolation
Finding non-linear data is very difficult compared to linear data because it is difficult to find the pattern. The FORECAST function shows good results for interpolating linear datasets. But for the non-linear datasets, the result is not up to the mark. And the GROWTH function works well for the exponential dataset. For this reason, we have formulated a new formula combining the FORECAST, INDEX and MATCH functions.
STEPS:
- Now, write down the following formula in the F6 cell:
=SLOPE(C5:C12,B5:B12)*F5+INTERCEPT(C5:C12,B5:B12)
- Then, press Enter to observe the interpolated result.
Download Practice Workbook
To practice by yourself, download the following workbook.
Conclusion
In this article, we have demonstrated how to do 2D interpolation in Excel. There is a practice workbook at the beginning of the article. Go ahead and give it a try. Last but not least, please use the comment section below to post any questions or make any suggestions you might have.
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