Linear interpolation in a table

Question

I have the following table:

How do I use linear interpolation to fill in the data under 400?

Answer 1

In MATLAB, you should use the function interp1.

From the help:

vq = interp1(x,v,xq) returns interpolated values of a 1-D function at specific query points using linear interpolation. Vector x contains the sample points, and v contains the corresponding values, v(x). Vector xq contains the coordinates of the query points.

For a given volume in your table, the sample points $x$ are the values 300 and 500, and the corresponding values $v(x)$ are the values in the columns: e.g., for volume equal to 1, $x=[300, 500]$, $v=[2494, 4157]$. As the query point xq you have 400. For each volume listed, you should call the function with the corresponding input arguments.

The default rule for interpolation is linear. However, others may be used if necessary. From the help:

vq = interp1(x,v,xq,method) specifies a string for choosing an alternative interpolation method: 'nearest', 'next', 'previous', 'linear','spline','pchip', or 'cubic'. The default method is 'linear'.