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array of function handle

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Simo
Simo on 12 Jun 2020
Commented: Walter Roberson on 13 Jun 2020
I have to convert a code written using syms, to a code with function handle. (my prof doesn't want me to use syms)
how can I select the element of the array?
I write a simpler code
A=@(x)[sin(x), cos(x);1, -1];
B=@(x)[sin(x);cos(x)];
C=@(x) A(x)*B(x); % this is an array of 2 element
D=@(x) C(first element) - C(second element)

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Accepted Answer

Walter Roberson
Walter Roberson on 12 Jun 2020
First = @(x) x(1);
Second = @(x) x(2);
D = @(x) First(C(x)) - Second(C(x));
However, this will execute C twice. More efficient would be
FirstMinusSecond = @(x) x(1) - x(2);
D = @(x) FirstMinusSecond(C(x))

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Simo
Simo on 13 Jun 2020
ok it works thanks, but if I want to plot D?
---------------------
l=linspace(0,3*pi);
plot(l,D(l))
--------------------
error:
--------------------
Error using vertcat
Dimensions of arrays being concatenated are not consistent.
Error in Untitled3 (line 3)
A=@(x)[sin(x), cos(x);1, -1];
Error in Untitled3 (line 5)
C=@(x) A(x)*B(x); % this is an array of 2 element
Error in Untitled3 (line 7)
D = @(x) FirstMinusSecond(C(x));
Error in Untitled3 (line 10)
plot(l,D(l))
Walter Roberson
Walter Roberson on 13 Jun 2020
Your A and B and C are only valid if x is a scalar, and your D would be unlikely to return the value you want if x is not a scalar. If you want to plot then instead of
plot(l,D(l))
do
y = arrayfun(D, l);
plot(l, y)

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