# Plot det(matrixA - (x * eye(3))) where x = 0:3

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Andrew Gapinski on 26 Nov 2017
Commented: Andrew Gapinski on 26 Nov 2017
I am new to MatLab and have been searching for a way to do plot this graph but cannot seem to figure it out.
Equation: det(matrixA - (x * eye(3))) where x = 0:3 and Matrix A is a predefined matrix
Error: Error using * Inner matrix dimensions must agree.
t = 0:3 Error in y1 = det(A1 - (t * eye(3)))
This equation as it stands is giving me an error everytime I run it and i think i understand where its coming from but am unsure how else to go about writing the equation any other way. I also need to be able to plot this for 4 different matrix A's on the same plot. Any help would be really appreciated! Thanks.

Walter Roberson on 26 Nov 2017
matrixA = rand(3); % do for some random matrix A
syms x
matdet = det(matrixA - (x * eye(3)));
fplot(matdet, [0 3])
Andrew Gapinski on 26 Nov 2017
Thanks for the quick response, I tried running this and am getting this error: Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym expression.
Andrew Gapinski on 26 Nov 2017
Nvm a simple clearvars worked. Thanks!