# How to extract output from function

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Ali Najem on 16 Nov 2020
Commented: Ali Najem on 18 Nov 2020
Hello, All
i have this functions file
function [dydt,dE]=my(x,y)
f=(x^2-y^2)*sin(x);
dE=x^2;
dydt=10+f;
end
and this my run file
a=1; b=2; ya=1; m=40;
f=(@(t,y)my(t,y));
[t,y]=pure(f,a,b,ya,m);
I need to obtain dE from the function how can i proceed this
thanks indeed..
this is pure function file
function [ts,ys] = pure(f,a,b,y0,N)
t0 = a; T = b;
h = (T-t0)/N;
ts = zeros(N+1,1);
ys = zeros(1,length(y0));
t = t0;
yold = y0;
ts(1) = t;
ys(1,:) = yold';
for i=1:N
s1 = f(t,yold);
ynew = yold + s1*h;
yold=ynew;
t = t + h;
ts(i+1) = t; ys(1,:) = yold';
end
end

Stephen Cobeldick on 16 Nov 2020
To get De you could use arrayfun:
a=1;
b=2;
ya=1;
m=40;
[t,y]=pure(@my,a,b,ya,m)
t = 41×1
1.0000 1.0250 1.0500 1.0750 1.1000 1.1250 1.1500 1.1750 1.2000 1.2250
y = 3.7363
[~,dE] = arrayfun(@(tv)my(tv,y),t)
dE = 41×1
1.0000 1.0506 1.1025 1.1556 1.2100 1.2656 1.3225 1.3806 1.4400 1.5006
function [dydt,dE]=my(x,y)
f=(x^2-y^2)*sin(x);
dE=x^2;
dydt=10+f;
end
function [ts,ys] = pure(f,a,b,y0,N)
t0 = a; T = b;
h = (T-t0)/N;
ts = zeros(N+1,1);
ys = zeros(1,length(y0));
t = t0;
yold = y0;
ts(1) = t;
ys(1,:) = yold';
for i=1:N
s1 = f(t,yold);
ynew = yold + s1*h;
yold=ynew;
t = t + h;
ts(i+1) = t; ys(1,:) = yold';
end
end

Ali Najem on 17 Nov 2020
This is it
for i = batches:batches+m-1
a1 = input(:,i);
z2 = w1*a1 + b1;
a2 = elu(z2);
z4 = w3*a2 + b3;
a4 = elu(z4);
e=(a4-y0(:,i));
error4 = e.*elup(z4);
errortot4 = errortot4 + error4;
error2 = (w34'*error4).*elup(z2);
errortot2 = errortot2 + error2;
end
dE2=errortot2;
dE4=errortot4;
w1=-u/m*dE1;
b1=-u/m*dE2;
w3=-u/m*dE3;
b3=-u/m*dE4;
dy1dt=[w1(:); b1(:); w3(:); b3(:)];
end
so, when i try the simple function like in my question i got dE correectly or even if i want more than one outputs now in this case same thing but i need to change my function.
i am also using:
[t,y]=pure(@my,a,b,ya,m)
now when i write this code
[~,dE1,dE2,dE3,dE4] = arrayfun(@(tv)my(tv,y),t)
when i run i got the error that i aforementioned
many thanks for helping me.
Stephen Cobeldick on 17 Nov 2020
This is how you defined the function my, with thirteen input arguments:
This is how you call the function my, with two input arguments:
my(tv,y)
If the function requires thirteen input arguments, then you need to call it with thirteen input arguments. You need to provide all of its required inputs, not just the first two.
Ali Najem on 18 Nov 2020
still got error am trying diffrent example same thing happening with me but with diffrent error
G=9.8; L=2;
tspan=[0 2*pi];
z0=[pi/3 0];
f=(@(t,y)my(t,y,G,L));
[t,y]=ode15s(f,tspan,z0);
[~,dE] = arrayfun(@(tv)mine(tv,y,G,L),t)
and this is the file of my function
function [dydt,dE]=my(t,y,G,L)
dydt = [y(2) ; -G/L*sin(y(1))];
dE=G*10;
end
when i run i got this error:-
Error using arrayfun
Non-scalar in Uniform output, at index 1, output 1.
Set 'UniformOutput' to false.
Error in run (line 18)
[r,dE] = arrayfun(@(tv)mine(tv,y,G,L),t)