Simulink Error "Attempt to extract field 'p1' from 'mxArray'"

I'm creating a parabolic curve fit then trying to send the parameters to another function block. It works in Matlab, but when I put it into function block

function coefficients  = my_block(Start, Steps, Setpoint)
coder.extrinsic('fit');
%#codegen

coefficients = [0;0;0];
x = [0; Steps; Steps*2];
y = [Start; Setpoint; Start];
f = fit(x,y,'poly2');

coefficients(1) = f.p1;
coefficients(2) = f.p2;
coefficients(3) = f.p3;

I get the error above. Simple fix?

Answer 1

[Swatantra Mahato]

Hi Dave,

The output of the extrinsic function 'fit' would be an mxArray, which is likely leading to the error when trying to extract 'p1' in the line

coefficients(1) = f.p1;

You can refer to the following link to work with output of an extrinsic function

https://www.mathworks.com/help/coder/ug/use-matlab-engine-to-execute-a-function-call-in-generated-code.html#bq1h2z9-46

Hope this helps