Matlab function input arguments problems

Hello.I would need some help with my university program. I needed to do a program on finite element method. I made it as a function with input arguments firstly, but now i want to input them from keyboard since i needed to add the program to a larger code with a menu in it and here's my problem. As soon as i did that the program went bananas and i get error at axis set and at second figure(2).

To make a general ideea, here's the code:

function []=Metoda_elementului_finit_cu_dreptunghiuri(a,b,c,d,N,M)

 close all
 clc
 % a=input('a=');
 % b=input('b=');
 % d=input('c=');
 % c=input('d=');
 % N=input('N=');
 % M=input('M=');

 x=linspace(a,b,N+1);
 y=linspace(c,d,M+1);
 hx=(b-a)/N; %pasul pe axa Ox
 hy=(d-c)/M; %pasul pe axa Oy

 % crearea matricii nodurilor
 Nod=zeros((N+1)*(M+1),3);
 k1=0;
 for j=1:M+1
   for i=1:N+1 
       k=i+(N+1)*(j-1);
       Nod(k,1)=x(i);
        Nod(k,2)=y(j);
        Nod(k,3)=0;
        if((i~=1)&&(i~=N+1)&&(j~=1)&&(j~=M+1))
            k1=k1+1;
            Nod(k,3)=k1;
        end
   end

 end
 display(Nod);

 %afisarea figurii pentru noduri
 figure(1)
 %construirea liniilor verticale
 for i=1:N+1
    plot(x(i)*ones(1,M+1),y)
    hold on
    %pause(0.2)
 end
 %construirea liniilor orizontale
 for j=1:M+1
    plot(x,y(j)*ones(1,N+1))
    hold on
    %pause(0.2)
 end
 %evidentierea nodurilor cu stelute sau cercuri
 for k=1:(N+1)*(M+1)
    if Nod(k,3)==0
        plot (Nod(k,1),Nod(k,2),'*b')%noduri exterioare
        hold on
    else
        plot(Nod(k,1),Nod(k,2),'or')%noduri interioare
    hold on
    end
    axis([a-0.2,b+0.2,c-0.2,d+0.2])
 end

 %matricea dreptunghiurilor
 Dr=zeros(N*M,4);
 kT=0;
 for j=1:M+1
    for i=1:N+1
        k=i+(N+1)*(j-1);%al catelea nod in numerotarea globala
        if(i<=N)&&(j<=M)
            kT=kT+1;
            Dr(kT,1)=k;
            Dr(kT,2)=k+N+1;
            Dr(kT,3)=k+N+2;
            Dr(kT,4)=k+1;           
        end
    end
 end
 display(Dr);

 %calculam MR si L
 MR=zeros((N-1)*(M-1));
 L=zeros((N-1)*(M-1),1);
 nd=N*M;
 %identificam coordonatele varfurilor dreptunghiului curent
 for k=1:nd
    xd=zeros(4,1);
    yd=zeros(4,1);
    for j=1:4
        xd(j)=Nod(Dr(k,j),1);
        yd(j)=Nod(Dr(k,j),2);
    end  
 %calculam coeficientii functiei psi,a(j),b(j),c(j),d(j)    
 D=zeros(4);
 for j=1:4
    D(1:4,j)=[xd(j)*yd(j);xd(j);yd(j);1];
 end
 Dinv=inv(D);
 A=Dinv(1:4,1);
 B=Dinv(1:4,2);
 C=Dinv(1:4,3);
 %calculam matricea termenilor liberii Me si Le
 Me=zeros(4);
 Le=zeros(4,1);
 ariaDr=(xd(3)- xd(1))*(yd(2)-yd(1));
 for i=1:4
    for j=1:4
        R=((A(i)*A(j)*(yd(2)^2 + yd(1)*yd(2) +...
            yd(1)^2 + xd(3)^2 + xd(3)*xd(1) + ...
            xd(1)^2 )*1/3)+(A(i)*B(j)+A(j)*B(i))...
            *(y(2)+y(1))+(A(i)*C(j)+A(j)*C(i))*(x(3)+...
            x(1))*1/2 +B(i)*B(j)+C(i)*C(j))*ariaDr;
        Me(i,j)=R;
    end
    Le(i)=(f(xd(i),yd(i))*ariaDr/4);
 end
 display(Me)
 display(Le)
 %se adauga Me si Le in MR si L(analog ca si in cazul triunghiurilor) 
 for i=1:4
    for j=1:4
        if((Nod(Dr(k,i),3)~=0) && (Nod(Dr(k,j),3)~=0))
            MR(Nod(Dr(k,i),3),(Nod(Dr(k,j),3)))=...
                MR(Nod(Dr(k,i),3),(Nod(Dr(k,j),3)))+Me(i,j);
        end
        if(Nod(Dr(k,i),3)~=0)
            L(Nod(Dr(k,i),3))=L(Nod(Dr(k,i),3))+Le(i);
        end
    end
 end
 end
 display(MR);
 display(L);
 %se rezolva sistemul MR*alpha=L
 alpha=inv(MR)*L; %sau MR\L se foloseste pentru calcul mai rapid
 display(alpha) 
 U1=zeros(N-1,M-1);
 for i=1:N-1
    for j=1:M-1
        k=i+(N-1)*(j-1);
        U1(i,j)=alpha(k);
    end
 end
 U=zeros(N+1,M+1);
 U(2:N,2:M)=U1;
  display(U)

%solutie exacta
figure(2)
[X,Y]=meshgrid(a:0.1:b,c:0.1:d);
 Z=2*sin(X).*sin(Y);
 display(Z)
 surf(X,Y,Z);

   %solutie aproximativa
   figure(3)
  [X,Y]=meshgrid(a:hx:b,c:hy:d);
  surf(X,Y,U');

 function[z]=f(x,y)
 z=2.*sin(x).*sin(y);
 end

 end

What i want to do exactly is remove all the input variable and uncomment the input ones below so i can add them from keyboard.

Answer 1

[Walter Roberson]

"I made it as a function with input arguments firstly, but now i want to input them from keyboard since i needed to add the program to a larger code with a menu in it and here's my problem."

Taking them from the keyboard using input() will not be compatible with using graphic menus. Your GUI should extract the values for the parameters from the appropriate GUI elements and then should call upon your existing routine. For example,

a = str2double(handles.a);
b = str2double(handles.b);
c = str2double(handles.c);
d = str2double(handles.d);
N = str2double(handles.N);
M = str2double(handles.M);
Metoda_elementului_finit_cu_dreptunghiuri(a,b,c,d,N,M);

[Milu Mihai]

Pardon me , but i do not understand what u mean.Perhaps i wasn't specify enough as well.I want to use this menu:

if true
  % function []=cap7()

 fprintf('CAPITOLUL 7: Aproximari numerice pentru probleme Dirichlet pe 
 R^2, pe dreptunghi\n')
 fprintf('\n')
 op=1;
 while(op~=0)
 fprintf('\n')
 fprintf('7.1. Metoda diferentelor finite\n')
 fprintf('7.2. Metoda elementului finit cu triunghiuri\n')
 fprintf('7.3. Metoda elementului finit cu dreptunghiuri\n')
 fprintf('7.0. End capitol 7\n')
 fprintf('\n')

 fprintf('Alege optiune capitol 7: ')
optiune_cap7=input('');
 switch optiune_cap7
    case 1 
        Metoda_diferentelor_finite_noduri()
    case 2 
        Metoda_elementului_finit_cu_triunghiuri();
    case 3 
        Metoda_elementului_finit_cu_dreptunghiuri();
    case 0 
        fprintf('Bye capitol 7\n')    

    otherwise
        fprintf('Optiune imposibila pentru capitolul 7\n')
 end
 fprintf('vrei sa faci alta optiune din acest capitol? Da=1 Nu=0\n')
op=input('');
 end

 end % end cap 7 
  end

to call my function with the same name but in it to input myself the paramethers.I did search online what str2double means since i never used it but i do not really understand where should i put it in the code...

[Steven Lord]

Write a separate function that prompts the user to input the values of the variables then uses those values as inputs to your computational function.

So if you had a function:

function c = addthem(a, b)
c = a+b;

you could call it directly in a program:

function z = performComputations
x = 17;
y = 42;
z = addthem(x, y);

or you could call it via the function that calls input.

function z = performComputationsInput
x = input('Enter number 1:');
y = input('Enter number 2:');
z = addthem(x, y);

Neither performComputations nor performComputationsInput require you to change the function that actually computes, addthem, to reflect where the data is coming from.

[Stephen23]

Better to use str2double:

function z = performComputationsInput
x = str2double(input('Enter number 1:','s'));
y = str2double(input('Enter number 2:','s'));
z = addthem(x, y);

[Milu Mihai]

So from what i understand i must do something like this:

if true

function z = performComputationsInput

 a=str2double(input('a=','s'));
 b=str2double(input('b=','s'));
 d=str2double(input('c=','s'));
 c=str2double(input('d=','s'));
 N=str2double(input('N=','s'));
 M=str2double(input('M=','s'));
 z = addthem(a,b,c,d,N,M);
 end

end

and then call the function like this

if true
  % function []=Metoda_elementului_finit_cu_dreptunghiuri(z)
end

? still doesnt work... I understand what you mean to do a function that stores variables beforehad but i do not understand how do i call back the variable back to use them in my main programm

[Stephen23]

The function addthem was an example. It is not a real function.

"I understand what you mean to do a function that stores variables beforehad"

No, there is no extra function storing the values beforehand. You only need your original function, which already is correct and works with input arguments.

The suggestion Walter Roberson made was to leave your original function unchanged (is would be very and design to replace the input arguments with input calls inside the function), something like this:

   a = str2double(input('a=','s'));
   b = str2double(input('b=','s'));
   d = str2double(input('c=','s'));
   c = str2double(input('d=','s'));
   N = str2double(input('N=','s'));
   M = str2double(input('M=','s'));
   Metoda_elementului_finit_cu_dreptunghiuri(a,b,c,d,N,M)

It really is that easy.

[Milu Mihai]

Damn it i'm really dumb.Ok i made it work just made a separate function for the variables as you said. Thanks alot for all the help everyone!