Understanding Interpolation

Interpolation is a method for estimating the value of a function between two known values. Often some relationship is measured experimentally or traced with Dagra at a range of values. Interpolation can be used to estimate the function for untabulated points.

For example, suppose we have tabulated data for the thermal resistance of a transistor tabulated for air velocity from 0 to 1800 FPM in 200 FPM steps. Interpolation can be used to estimate the thermal resistance at non-tabulated values such as 485 FPM.

Linear Interpolation

Linear interpolation involves estimating a new value by connecting two adjacent known values with a straight line.

If the two known values are (x1, y1) and (x2, y2), then the y value for some point x is:

Note: Linear interpolation works best when the function is not changing quickly between known values. It is probably not the best choice in this example because we don't have many tabulated points. Dagra, however, will provide enough data points for accurate linear interpolation.