## Cant find the number of row for big size of matrix

### fyza affandi (view profile)

on 4 Jan 2019
Latest activity Commented on by madhan ravi

on 4 Jan 2019

### per isakson (view profile)

I have a tblBarray matrix of size 13x1
1
3
2
5
4
10
8
11
12
14
15
16
21
and from given list of E3,
Columns 1 through 18
1 1 4 5 1 1 3 1 1 1 2 5 1 1 1 1 3 4
Columns 19 through 36
1 3 5 10 5 4 4 2 3 4 5 8 4 1 1 2 12 16
Columns 37 through 54
1 1 3 3 1 2 10 14 1 1 1 1 1 1 10 8 2 5
Columns 55 through 64
3 15 5 2 1 3 2 21 1 11
I need to search which row thet are belong to that tblBarray
I use this code below
for nE3=1:length (E3)
e31= find(E3(nE3)==tblBarray);
e3=[e3,e31];
end
1 1 5 4 1 1 2 1 1 1 3 4 1 1 1 1 2
Columns 18 through 34
5 1 2 4 6 4 5 5 3 2 5 4 7 5 1 1 3
Columns 35 through 51
9 12 1 1 2 2 1 3 6 10 1 1 1 1 1 1 6
Columns 52 through 64
7 3 4 2 11 4 3 1 2
Then I try for a bigger size of tblBarray unfortunately, it takes a very long time. Can anyone help me how can I solve this? Do i need to change 'find' function? If so, how can I change it?

### per isakson (view profile)

on 4 Jan 2019
Edited by per isakson

### per isakson (view profile)

on 4 Jan 2019

The editor warns you that there is an issue with your code.
• Notice the orange signs in the column to the right of the editor text pane.
• The variable e3 is underlined
Right click the underlined e3
If you have not already preallocated e3, you shall do that.
Compare the speed of your loop with this one
%%
e3 = nan( size(E3) );
for nE3=1:length (E3)
e3(nE3) = find(E3(nE3)==tblBarray);
end

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fyza affandi

### fyza affandi (view profile)

on 4 Jan 2019
Thank you so much :)
per isakson

### per isakson (view profile)

on 4 Jan 2019
Matlab for-loops have a reputation for being slow. However, nowadays they are much faster than they used to be. In your case, I guess the problem is find, especially if tblBarray is large.
Compare the speed with the solution of madhan ravi . I guess that one is faster.

on 4 Jan 2019
+1 debugging skills are real good!