Index exceed matrix dimension error

Everytime time that I run my code, this error ocurrs:

Index exceeds matrix dimensions.

Error in analyse_lbbc (line 17)

m_flow(:,i)= v_flow(:,i)*de;

what should I do ? Thank You

function [v_flow,m_flow,v1,F_1,F_2,F_1_mean,F_2_mean]= analyse_lbbc(m,v,t);

%create some variable

m=[0.4 0.3 0.2 0.1]; 

v=[0.003;0.003;0.003;0.003];

t=[11.3 11.8 16.8 20.4];

%save the variable m,v,t into one *.mat file

save data.mat m v t

%load the data

load data.mat 

d= 0.005; %diameter

de=0.001; %density of the water

g=9.81; %gravity 

A=(pi/4)*(d^2); %cross section area of the nozzle

c=0

for i=1:4

     v_flow(i,:)= v(i,:)./t(:,i);
     m_flow(:,i)= v_flow(:,i)*de;
     v1=v_flow(:,i)*A;

     F_1= m(:,i)*g;
     F_2= m_flow(:,i).*v1(:,i); 
  end
  F_1_mean = mean(:,1:4);
  F_2_mean= mean(:,1:4);
  c=F_1_mean - m(:,1:4)*F_2_mean;

Answer 1

[Walter Roberson]

Look more closely at your code. You have

     v_flow(i,:)= v(i,:)./t(:,i);
     m_flow(:,i)= v_flow(:,i)*de;

In the first line you write into the i'th row of v_flow, but in the second line you read from the i'th column of v_flow. If your v_flow does not happen to contain at least 4 columns then reading from the i'th column would be index exceeding matrix dimensions.

Answer 2

[Geoff Hayes]

Leticia - the error message Index exceeds matrix dimensions is telling you that the code is trying to access an element within a matrix using an index that exceeds the dimensions of that matrix. So put a breakpoint at line 17 (or your code)

 m_flow(:,i)= v_flow(:,i)*de;

and call your function. When the debugger pauses at this line look at the value of i and the dimensions for m_flow and v_flow. Does accessing the ith column of v_flow make sense?

[Leticia Campello]

So, should I create another function before writing m_flow(:,i)= v_flow(:,i)*de; ? I am really stuck with this because this afternoon was working and now it is not working anymore!!

[Geoff Hayes]

Leticia - when you step through the code, what are the dimensions of m_flow and v_flow? What is the i that is causing the problem? I don't have access to your data so cannot comment on why you are observing this error or whether another function is needed.