# Finding the index of spesific element in a matrix?

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IBM watson on 23 May 2019
Commented: Ulika Naidoo on 22 Jan 2021 at 9:28
Lets say we have matrix:
a=[ 2, 3, 5
3, 4, 7
4, 4, 4] ;
I want to know index of a(4) which is the bold 3. This is just an example. I want to learn how to find index of a(n).

madhan ravi on 23 May 2019
Edited: madhan ravi on 23 May 2019
Assuming you want to index of the last match in the matrix:
Index=find(a==3,1,'last')

IBM watson on 23 May 2019
That's it! Thak you so much.
But I can't find the index of them right? as columns and rows. Just curious.
madhan ravi on 23 May 2019
No problem, by the way the original question you asked is totally irrelevant to your latter comment. Please don’t do this in the future riddling the answers.
Look into ind2sub() function to convert the linear indices. To understand what this statement means , you need to read the link which I shared thoroughly and practice. And finally have a look at ind2sub().
IBM watson on 23 May 2019
Sure, I didn't do it on purpose. Just could't explain clearly what I want. Thanks again.

KALYAN ACHARJYA on 23 May 2019
Edited: KALYAN ACHARJYA on 23 May 2019
I want to know index of a(4) which is the bold 3
here ......................... this 4^ represent the index, I guessing you are looking for following one.
idx=find(a==3);
One dimentional case array case
>> a=[2,3,5,3,4,7,4,4,4];
>> idx=find(a==7)
idx =
6
>> idx=find(a==3)
idx =
2 4
But Matrices have 2 dimention so indices represents (x,y), where answer will be little different
>> a=magic(3)
a =
8 1 6
3 5 7
4 9 2
>> [r c]=find(a==3)
r =
2
c =
1

mohamed essabir on 5 Mar 2020
why c =1 ?
Stephen Cobeldick on 5 Mar 2020
"why c =1 ? "
Because the value 3 is in the 1st column.
Ulika Naidoo on 22 Jan 2021 at 9:28
Thank you!