MATLAB: How to reduce dimension of griddedinterpolant

girdded dataMATLAB

I have a gridded efficiency map where each point depends on different input values for current and voltage.
F = griddedInterpolant(x_voltage,y_current,eff_map)
% and query points 
eff = F(voltage_set,current_set)
Now I want to convert this map while runtime of a program to a curve for a fixed voltage, so that the efficiency just depends on the current/power.
Kind of,
function new_F = reduceDimension(F,fixed_voltage)
    ...
end
eff = new_F(power_set)
I can't find a quick solution, maby someone has an idea.
THX

Best Answer

whos
  Name             Size               Bytes  Class     Attributes
  eff_map        500x500            2000000  double              
  x_voltage      500x500            2000000  double              
  y_current      500x500            2000000  double
We are given some data as arrays, and you understand how to use griddedInterpolant. What you need to learn next is about building a function handle.
F = griddedInterpolant(x_voltage,y_current,eff_map)
Now, you want to reduce that, for a FIXED voltage, to a function of only one variable. Since 42 is the answer to everything, I'll fix the voltage at 42.
FixedVolts = 42;
F_v42 = @(y) F(repmat(FixedVolts,size(y)),y);
That is all it takes. We can now evaluate the new function at some value or a list of values for the current. We can even plot it as a function of one variable now. I've even set up F_42v in such a way that we can even pass in a complete vector or array for y. The result will be the same shape and size as the input for y.
F_v42(17)
ans =
         0.881963765526607
         
F_v42([1 3 5])
ans =
        0.0952082740655224         0.230322190630928         0.381508409480828
         
fplot(F_v42,[0,50])
xlabel 'y_current'
ylabel 'eff_map @ x = 42'
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