How to reduce dimension of griddedinterpolant?

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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

采纳的回答

John D'Errico
John D'Errico 2020-7-29
编辑:John D'Errico 2020-7-29
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'
  1 个评论
Konrad Warner
Konrad Warner 2020-7-29
Perfect, thanks!
Just, to get rid of the original map data I create a new griddedInterpolant with reduced dimentions by using output arguments of fplot, or speaks something against it?
[x,y] = fplot(F_v42,[0,50])
F_v42 = griddedInterpolant(x,y)
The result looks fine, but I get a lot of warnings using fplot. No idea what that means.
Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your
function to return an output with the same size and shape as the input arguments.
> In matlab.graphics.function.FunctionLine>getFunction
In matlab.graphics.function/FunctionLine/updateFunction
In matlab.graphics.function.FunctionLine.set.Function_I
In matlab.graphics.function.FunctionLine.set.Function
In matlab.graphics.function.FunctionLine
In fplot>singleFplot (line 245)
In fplot>@(f)singleFplot(cax,{f},limits,extraOpts,args) (line 200)
In fplot>vectorizeFplot (line 200)
In fplot (line 166)
Warning: Having two output arguments for fplot will be removed in a future release. Use the XData and YData
properties instead.
> In fplot (line 180)

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