Excluding elements from array

I need help trying to exclude values past position 19 from an array of 295. I have tried using the exlude command but was unable to understand the syntax. The array is converted from a table of data into StrainA. Then the data is checked to see at which point the graph is non-linear. I then only want to graph the regression line for that data. WhennonLinear = 19 for this data set. I cannot send the data file.

Example:

Force = TensileTestData(:,7);
Area = 4 * .25;

Stress = Force ./ Area;
Strain = TensileTestData(:,6);

StrainA= table2array(Strain);
StressA =table2array(Stress);

PositionNonLin = ischange(StressA,'linear', 'MaxNumChanges',1);
WhennonLinear = find(PositionNonLin==1);

RegStrainA = exclude(StrainA,[:,WhennonLinea:end]);

Regression = fitlm(RegStrainA,StressA);

figure(1)
hold on
scatter(StrainA, StressA)
plot (Regression)
title('Tensile Test')
xlabel("Strain")
ylabel("Stress")
hold off

[Voss]

By the way, you can get the values out of the table directly by using curly braces instead of parentheses:

Force = TensileTestData{:,7};
Area = 4 * .25;

StressA = Force ./ Area;
StrainA = TensileTestData{:,6};

Then you can omit the table2array lines.

Answer 1

[Voss]

WhennonLinear = find(PositionNonLin==1);

Regression = fitlm(StrainA(1:WhennonLinear-1),StressA(1:WhennonLinear-1));