MATLAB: For loops not working

for looploop

The below code is to calculate the modes on a plate. The for loops are not using all the values of m & n

% Modes on a plate
Lx=0.286; % length of plate(m)
Lz=0.198; % breadth of plate(m)
for m = 1:1000 % mode numbers
  for n = 1:10
    func=((n.*pi)./Lx).^2 +((m.*pi)./Lz).^2;% summation function n=1:10 & m= 1:1000
  end
end

Best Answer

The same goal can be achieved trivially using meshgrid() or ndgrid() without a loop:

% Modes on a plate
Lx=0.286; % length of plate(m)
Lz=0.198; % breadth of plate(m)
n=10;
m=1000;
[Y,X]= ndgrid(1:m,1:n);
func=(X*pi/Lx).^2 +(Y*pi/Lz).^2;

But the modication in your code is as follows:

func = zeros(1000,10); % before loop
func(m,n) = ... %just add (m,n) next to func inside the loop

Related Solutions

MATLAB: Reduction of repeated lines in code

This should do:

dfunc = zeros(1000,1000,10) ; 
for n = 1:10
    dfunc(:,:,i) = (sin(2.*pi*x0/Lx).*sin(m.*pi.*z0/Lz).*sin((n.*pi.*X)/Lx).*sin(m.*pi.*Z/Lz)).*exp(1j*wp*t)./(-wp^2+wnm(n,:).*(1+1j*eta));
end

The whole code:

clc; clear all ;
%% 1a velocity 0-1kHz
Lx=0.286; % length of plate(m)
Lz=0.198; % breadth of plate(m)
h=3.25e-3;% thickness of plate(m)(also d)
E=1.4e9 ;%Youngs modulus
M=265*h;%Mass per unit area( rowS surface density)
mu=0.3;%Poisson?s ratio
eta=4e-2;%Damping Factor
x0=0.16;%exc=(0.16,0.083), point of excitation(m)

z0=0.083;%exc=(0.16,0.083), point of excitation(m)
F=1;% Point load assumed to be 1 newton @ (x0,z0)
f=linspace(1000,1,10); % frequency array
w=2*pi.*f;% angular frequency array
t=1; %  time 
m=1:1000;% mode numbers width
n=10; % mode numbers length
func=zeros(n,length(m));% initial values as place holders
for i=1:n 
func(i,:)=(i*pi./Lx).^2 +(m*pi/Lz).^2; % modes for m=1:1000 & n=1:10
end
D=E*h^3/(12*(1-mu^2));% flexural density D eq 86 Notes
wnm=sqrt(D/M)*func; % for loop for wnm is not required as it ia a scalar multiple of func
 
% for all frequencies common vfunc is defined. vfunc is multi-dimensional
% array with dimensions as 10,10,1000. 
vfunc=zeros(length(w),n,length(m));% 3D array initial values as place holders
for k=1:length(w)
for i=1:n
vfunc(k,i,:)= 1j*w(k)*((sin(i*pi*x0/Lx).*sin(m.*pi*z0./Lz)).^2./(-w(k)'.^2 ...
                        +wnm(i,:).^2.*(1+1j*eta))).*exp(1j.*w(k).*t);          % velocity function  
end
end
v=(4/(Lx*Lz))*(F/M)*vfunc; %diffrentiated Eq 98 Notes
vSum=squeeze(sum(v,2)); % squeeze-removes the singleton dimension
RlvSum=sum(real(vSum),2);% vector of all modes at chosen freq array
figure('NumberTitle','off','Name','Velocity 0-1kHz')
plot(f,RlvSum);
xlabel('Frequency Hz')
ylabel('Velocity m/s')
 
 
 
%% 1b Displacement plot 
xr=linspace(0,Lx,1000);% 1000 x co-ordinate points on surface
zr=linspace(0,Lz,1000); % 1000  z co-ordinate points on surface
wp=2*pi*500; % pressure plot @ 500 Hz
[X,Z]=meshgrid(xr,zr);% plane to be plotted on 
dfunc = zeros(1000,1000,10) ; 
for n = 1:10
    dfunc(:,:,i) = (sin(2.*pi*x0/Lx).*sin(m.*pi.*z0/Lz).*sin((n.*pi.*X)/Lx).*sin(m.*pi.*Z/Lz)).*exp(1j*wp*t)./(-wp^2+wnm(n,:).*(1+1j*eta));
end
dt1 = sum(dfunc,3) ; 
ydt=(4/(Lx*Lz))*(F/M).*real(dt1);% displacement due to all modes
figure('NumberTitle','off','Name','Displacment @ 500 Hz')
surf(X,Z,ydt,'EdgeColor','interp');
view(-90,90)
xlabel('Length')
zlabel('Displacement')
ylabel('Width')
colorbar

MATLAB: For loop nested in while loop problem

I realized that I didn't reinitialize my "a" variable, thanks to Barmar's comment. Although the code might not look very efficient, this is what works for me:

    a = 10;
    k = 0.5;
    n = 2;
    while a < 300
        a = 10;
        for m = 1:5
            a = a + (a*k) + n;
        end
        if a >= 300
            break
        end
        n = n + 1;
    end

Best Answer

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MATLAB: Reduction of repeated lines in code

MATLAB: For loop nested in while loop problem

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