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"Z must be a matrix, not a scalar or vector." PLEASE HELP!

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So this is the function I want graph using surf.m:
%simple multivariate function;
function [f]=ps2func(x1,x2)
if ((x1<=2) &&(x2<=2))
f=4.*x1+3.*x2; %case 1 for the function
elseif ((x1>2) &&(x2>2))
f=x1.^2+x2.^2; %case 2 for the function
else
f=0; %case 3 for the function
end
%this is the suf.m function i used in an attempt to graph it:
x1 = 1:.1:4;
x2 = 1:.1:4;
[X,Y] = meshgrid(x1,x2);
Z= [f];
mesh(X,Y,Z)
grid on
hold on

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Accepted Answer

Matt J
Matt J on 27 Sep 2020
Edited: Matt J on 27 Sep 2020
You should have something like this:
x1 = 1:.1:4;
x2 = 1:.1:4;
mesh(x1,x2, ps2func(x1,x2) );
grid on
hold on
function f=ps2func(x1,x2)
if isvector(x1), x1=x1(:);x2=x2(:).'; end
f1=4.*x1+3.*x2; region1=(x1<=2) & (x2<=2);
f2=x1.^2+x2.^2; region2=(x1>2) & (x2>2);
f=false(size(f2));
f(region1)=f1(region1);
f(region2)=f2(region2);
end

More Answers (1)

Rafael Hernandez-Walls
Rafael Hernandez-Walls on 27 Sep 2020
x1 = 1:.1:4;
x2 = 1:.1:4;
[X,Y] = meshgrid(x1,x2);
Z= ps2func(X,Y);
mesh(X,Y,Z)
grid on
hold on
function [f]=ps2func(x1,x2)
f=size(x1);
f=((x1<=2)&(x2<=2)).*(4.*x1+3.*x2)+((x1>2)&(x2>2)).*(x1.^2+x2.^2);

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