Interpolate 1D vi

[slh3mm]

I'm fairly new to LabView and I'm trying to use Interpolate 1D.vi to calculate the dBm loss at certain frequencies that are different from the frequencies that are measured experimentally. I've successfully been able to generate the correct losses at my measurements, but I now need to subtract the loss at each frequency from the measured power at each frequency (actual power = measured power - loss basically). What is the best way to do this? My idea was to loop through my measured power array and subtract the loss, but since the Interpolate 1D.vi has a separate output for the xi used, I'm not sure if my approach would work since every frequency may/may not be included.

[altenbach]

Can you also attach your data file so we have something to play with?

I recommend to "save for previous" before attaching. Many don't have LabVIEW 2021 yet. You should also make typical values for the "Measured Freqs (GHz)" default before saving so we know what typical values are (enter data...select array (not element!)...edit...make selected values default...save VI).

Where is the control for "measured power" for each frequency?

(I am not sure why you are using such a convoluted way to get the first two columns?)