How to extract output from function

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

Answer 1

[Stephen Cobeldick]

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]

thank you so much for your answer

it worked....

there is thing when i try to obtain more than one output such as:-

[~,dE1,dE2,dE3,dE4] = arrayfun(@(tv)my(tv,y),t)

i got this error Not enough input arguments.

is that any thing i suppose to change for this case

many thanks .

[Stephen Cobeldick]

@Ali Najem : please post the complete error message. This means all of the red text.

[Ali Najem]

Not enough input arguments.

Error in Run>@(tv)my(tv,Y1) (line 57)
[~,dEdw12,dEdb12,dEdw34,dEdb34]=arrayfun(@(tv)my(tv,Y1),T1);

Error in Run (line 57)
[~,dE1,dE2,dE3,dE4]=arrayfun(@(tv)my(tv,Y1),T1);

this is the error that i got if i need to call more than one outputs

[Stephen Cobeldick]

@Ali Najem : please post the code of the function my that you are using, and the output of this command:

which my -all

[Ali Najem]

This is it

function [dy1dt,dE1,dE2,dE3,dE4] =my(input,batches,m,w1,b1,w3,b3,y0,u,errortot4,errortot2,grad4,grad2)
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;
grad4 = grad4 + error4*a2';
error2 = (w34'*error4).*elup(z2);
errortot2 = errortot2 + error2;
grad2 = grad2 + error2*a1';
end       
dE1=grad2;
dE2=errortot2;
dE3=grad4;
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]

This is how you defined the function my, with thirteen input arguments:

function [dy1dt,dE1,dE2,dE3,dE4] =my(input,batches,m,w1,b1,w3,b3,y0,u,errortot4,errortot2,grad4,grad2)

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.

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[Ali Najem]

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)