Error using / Matrix dimensions must agree...

Below is my script:

>> clf
>> hold on
>> axis([-1 1 -1 1])
>> x=-1:0.0001:1;
>> y=cos(1/x)
>> plot(x,y)

May I know why I keep getting this error:-

(Error using  /  Matrix dimensions must agree...)?

[guadalupe presa]

kEST=(s/(n+g+d))^(1/(1-alfa)); % realiza un código (k*)=steady state (NIVEL DE CAPITAL DE EQUILIBRIO)

SteadyState=findobj('Tag','STEADYSTATE'); set(SteadyState,'String',kEST);

upper=ceil(kEST)*2; jump=upper/10; k=(0:jump:upper)';

ec1=(n+g+d).*k; %ecuación 1= capital consumido: (n+g+d)*k (RECTA - FUNCION DE PRODUCCION) ec2=s.*k.^alfa; %ecuación 2= de capital acumulados:s*k^alfa (CURVA - FUNCION DE INVERSIÓN)

error: Error using / Matrix dimensions must agree.

Error in MODELOSOLOWCURVASFASE (line 87) kEST=(s/(n+g+d))^(1/(1-alfa)); % realiza un código (k*)=steady state (NIVEL DE CAPITAL DE EQUILIBRIO)

Answer 1

[Amit Nambiar]

It should be like this: >> clf >> hold on >> axis([-1 1 -1 1]) >> x=-1:0.0001:1; >> y=cos(1./x) >> plot(x,y)

always use .* ./ (mul and div resp)for element by element operations. And use * / without "." for matrix operations.

Answer 2

[Matt J]

 y=cos(1./x)

Answer 3

[Image Analyst]

element by element operations

Answer 4

[Mugisha Aime]

Matrix dimensions must agree.

[Image Analyst]

We know the error. The reason was that they used matrix division instead of element-by-element division. In other words, he used slash

y=cos(1/x)  % Not right.

instead of dot slash

y=cos(1 ./ x)  % This is the fix.

as we informed Austin 4 years ago.

[Muhammad Azrul Izmee]

This is not right too.. I hv do it but keep getting error

[Image Analyst]

@Muhammad Azrul Izmee, it is right. Here's proof

x=-1:0.0001:1;
y=cos(1 ./ x)

y = 1×20001

0.5403 0.5402 0.5401 0.5400 0.5400 0.5399 0.5398 0.5397 0.5396 0.5395 0.5395 0.5394 0.5393 0.5392 0.5391 0.5390 0.5390 0.5389 0.5388 0.5387 0.5386 0.5385 0.5384 0.5384 0.5383 0.5382 0.5381 0.5380 0.5379 0.5379

plot(x, y, 'b-')

See? No error.

You should start a new question with your own code.

Answer 5

[moahaimen talib]

hi please i need your help i need to process many images into wavelet function

yFolder = 'images';
  if ~isdir(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
    uiwait(warndlg(errorMessage));
    return;
  end
  filePattern = fullfile(myFolder, '*.jpg');
  jpegFiles = dir(filePattern);
  for k = 1:length(jpegFiles)
    baseFileName = jpegFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf(1, 'Now reading %s\n', fullFileName);
    imageArray = imread(fullFileName);
     figure(k);imshow(imageArray);  % Display image.
     drawnow; % Force display to update immediately.
   [coeffa,coeffh,coeffv,coeffd]=wavelet_process(imageArray);

i recieve this error

Error using + Matrix dimensions must agree.

Error in idwt2 (line 89) x = upsconv2(a,{Lo_R,Lo_R},sx,dwtEXTM,shift)+ ... % Approximation.

Error in wavelet_inv_process (line 5) resimg=idwt2(coeffa,coeffh,coeffv,coeffd,'haar');

Error in top_run2 (line 74) inv_wave_img=wavelet_inv_process(coeffa,imgadjh,imgadjv,imgadjd);

please SOS

Answer 6

[ahmed reda]

i want to know the error of this code iwant to plot w with X&Y and this error is founed

clear ;
clc;
close all;
    R=0.01;                              %Shaft radius
    m=1.675;                             %Disc mass (Kg)
    L=0.5;                               %Shaft Length (m)
    E=210*10^9;                          %Modulus of elasticity (N/m^2)
    Ro=7850;                             %Density (Kg/m^3)
    Ix=(1/4)*pi*R^4;                     %Moment of Inertia (Kg.m^2)
    A=pi*R^2;                            %Cross section area (m^2)
    K=48*E*Ix/L^3;                       %Shaft Stiffness simply supported (N/m)
    Z=0.00125;                            %Damping ratio 
    C=Z*2*sqrt(K*m);                     %Damping constant (N/m)
    e=0.059665;                          %eccentricity (m) 
    N=1500;                              %(rpm)
    w=(0:.5:30);                          %rotational speed (rad/sec)
    Wn=sqrt(K/m);                        % natural frequency
%     h=0.001;                             %time step (sec)
    g=9.81;
    O=m*g/K;                             %Initial deflection
    T=5;fs=5*8*w/(2*pi); dt=1/fs;         %sampling frequency 
    tspan=(0:dt:T);                      %time interval
%     X0 = [0 0];                          %Initial displacement, Initial velocity in X direction 
%     Y0 = [O 0];                          %Initial displacement, Initial velocity in y direction 
%     [~,X]=ode45(@abdo,tspan,X0,[],m,K,C,w,e);
%     [t,Y]=ode45(@reda,tspan,Y0,[],m,K,C,w,e);
    X=(m*e*(w*w))/sqrt((K-m*(w*w))^2+(C*w)^2);
    Y=(m*e*(w*w))/sqrt((K-m*(w*w))^2+(C*w)^2);
    plot(w,X);grid;xlabel('W(rad/sec)');ylabel('X');
    figure
    plot(w,Y);grid;xlabel('W(rad/sec)');ylabel('Y');

The error is:

Error using /

Matrix dimensions must agree.

Error in amplitudewithfrequency (line 21)

T=5;fs=5*8*w/(2*pi); dt=1/fs; %sampling frequency

[Image Analyst]

When you get an error like that you should put each line of code on it's own line:

T=5;
fs = 5*8*w /(2*pi); 
dt=1/fs;         %sampling frequency

so now you'll see it's 1/fs that is the problem. And fs is a vector since you made w a vector. So maybe you need to rethink that dt is. Maybe it's 1 ./ (fs(2)-fs(1)) or something like that.

[Ninad Bhagwat]

Hello,

I tried using both / and ./ but I am still getting the error. Can you please tell me what should I do?

[Image Analyst]

Ahmed and Ninad:

What you needed to do was to make up a list of w's and then in a for loop compute the values for each one of those w values. I believe this answers it:

clear ;
clc;
close all;
R = 0.01;                              %Shaft radius
m = 1.675;                             %Disc mass (Kg)
L = 0.5;                               %Shaft Length (m)
E = 210*10^9;                          %Modulus of elasticity (N/m^2)
Ro = 7850;                             %Density (Kg/m^3)
Ix = (1/4)*pi*R^4;                     %Moment of Inertia (Kg.m^2)
A = pi*R^2;                            %Cross section area (m^2)
K = 48*E*Ix/L^3;                       %Shaft Stiffness simply supported (N/m)
Z = 0.00125;                            %Damping ratio
C = Z*2*sqrt(K*m);                     %Damping constant (N/m)
e = 0.059665;                          %eccentricity (m)
N = 1500;                              %(rpm)
wList = (0:.5:30);                          %rotational speed (rad/sec)
for k = 1 : length(wList)
	w = wList(k);
	Wn = sqrt(K/m);                        % natural frequency
	%     h = 0.001;                             %time step (sec)
	g = 9.81;
	O = m*g/K;                             %Initial deflection
	T = 5;
	fs = 5*8*w/(2*pi);
	dt = 1./fs;         %sampling frequency
	tspan = (0:dt:T);                      %time interval
	%     X0 = [0 0];                          %Initial displacement, Initial velocity in X direction
	%     Y0 = [O 0];                          %Initial displacement, Initial velocity in y direction
	%     [~,X] = ode45(@abdo,tspan,X0,[],m,K,C,w,e);
	%     [t,Y] = ode45(@reda,tspan,Y0,[],m,K,C,w,e);
	X(k) = (m*e*(w*w))/sqrt((K-m*(w*w))^2+(C*w)^2);
	Y(k) = (m*e*(w*w))/sqrt((K-m*(w*w))^2+(C*w)^2);
end
subplot(1, 2, 1);
plot(wList, X, 'b.-', 'MarkerSize', 12);
grid;
xlabel('W(rad/sec)');
ylabel('X');

subplot(1, 2, 2);
plot(wList, Y, 'r.-', 'MarkerSize', 12);
grid on;
xlabel('W(rad/sec)');
ylabel('Y');

[Rafli Noorsyaif]

clc

clear all

close all

%Diketahui (E1,E2,G12 dalam satuan MPa)

E = 180000;

SIGMAY = 502;

%S,A,W dalam satuan m

S = 0.1;

a = 0.005;

W = 0.01:0.01:0.1;

K = ((3*(S/W)*sqrt(a/W))/(2*(1+2*(a/W))*((1-(a/W))^(3/2))))*(1.99-(a/W)*(1-(a/W)))*(2.15-3.93*(a/W)+2.7*((a/W)^(2)))

Displacement = (K^(2))/(E*SIGMAY)

I have the same problem (Matrix dimensions must agree) on the line 14

K = ((3*(S/W)*sqrt(a/W))/(2*(1+2*(a/W))*((1-(a/W))^(3/2))))*(1.99-(a/W)*(1-(a/W)))*(2.15-3.93*(a/W)+2.7*((a/W)^(2)))

[Image Analyst]

Rafli, usually what many/most people do in situations like this, which have an incredibly complicated and involved equation, is to break it down into smaller parts, then examine the size of each term. Like

term1 = 3*S/W;
term2 = sqrt(a/W);

and so on. Just basic debugging technique.

Then make sure all your matrix multiplication dimensionss of each term make sense, and also make sure you really want to do a matrix multiplication with star and not an element-by-element multipliication with dot star.For example since you have term1*term2, that means the number of columns in term1 must equal the number of rows in term1 for a matrix multiplication since term1 is on the left side.

Start your own question if you still have trouble.

Answer 7

[Rahayu A Halim]

Hello, please I need your help

my script:

%____________________________________________________________________
function fx=obj_pid_ga(x)
global Kp Ki Kd
%
%
Kp=x(1);Ki=x(2);Kd=x(3);
%
%____________________________________________________________________
[t,~,y]=sim('model_sistem_PID',0:0.05:10);
%____________________________________________________________________
%Integral of Squared Error
fx=sum(t.*abs(y).^2);

May I know why I keep getting this error:

Error using .* 
Matrix dimensions must agree.

Error in obj_pid_ga (line 10)
fx=sum(t.*abs(y).^2);