logical index replace values

Hi

mBall(1:15001,4) = 0;
-3.42	-24.55	5.19	0
-3.01	-24.59	5.66	0
-2.59	-24.64	6.11	0
-2.19	-24.69	6.53	0
-1.78	-24.73	6.91	0
-1.38	-24.79	7.28	0
-0.98	-24.84	7.63	0
% this is what an exsample of what my mBall looks like 

% I have an array c that consist of 3786x2
% I'm trying to insert values from c(:,2) in mBall(:,4)
% But only in the rows equal to value in c(:,1)
c = 
2    1
3    1
4    2
5    3
7    3
% mBall should look like this afterwards
mball =
-3.42	-24.55	5.19    0
-3.01	-24.59	5.66    1
-2.59	-24.64	6.11    1
-2.19	-24.69	6.53    2
-1.78	-24.73	6.91	3
-1.38	-24.79	7.28	0
-0.98	-24.84	7.63	3

[madhan ravi]

Please illustrate with a short example.

[Morten Jørgensen]

Hi,

% I have an array c that consist of 3786x2

mBall(1:15001,4) = 0;
-3.42	-24.55	5.19	0
-3.01	-24.59	5.66	0
-2.59	-24.64	6.11	0
-2.19	-24.69	6.53	0
-1.78	-24.73	6.91	0
-1.38	-24.79	7.28	0
-0.98	-24.84	7.63	0
% this is what my mBall looks like 
% I'm trying to insert values from c(:,2) in mBall(:,4)
% But only in the rows equal to value in c(:,1)

c = 
2    1
3    1
4    2
5    3
7    3

% mBall should look like this
mball =
-3.42	-24.55	5.19    0
-3.01	-24.59	5.66    1
-2.59	-24.64	6.11    1
-2.19	-24.69	6.53    2
-1.78	-24.73	6.91	3
-1.38	-24.79	7.28	0
-0.98	-24.84	7.63	3

[madhan ravi]

I have no idea why some people make even a simple problem harder to be understood.

[Morten Jørgensen]

i'm sorry. i have tried to make it simple? is this okay ?

but how should the code look like then?

[madhan ravi]

Rows equal to c(:,1) show us how they are matched. It’s not clear.

[Morten Jørgensen]

yes, how should I then put the value into mBall(:,4)?

[Morten Jørgensen]

previously I have used function find like this

[xlocs, ylocs] = find(0 < output & output < 1);
c = [xlocs, ylocs]

% then i have my array mBall, that i want to change
mBall(1:15001,4) = 0;
% I want to replace the 0 in column 4 of mBall with the numbers in ylocs?
% is this more clear? 

Answer 1

[KSSV]

Read about logical indexing.

idx = 0 < output5 & output5 < 1 ;
output = output5(idx);

[KSSV]

If you want row number find(idx)