# Counting repeated values paired with other repeated values and placing those counts in an array

2 views (last 30 days)
Marianne on 15 Aug 2012
I have a dataset in which different stimulus levels are presented multiple times. So far I've managed to boil this down using unique and arrayfun to produce one column of unique values and a second column stating how many times the unique value was presented during the experiment. Here's my code for that, which I obtained through looking in MATLAB's FAQs regarding unique:
if true
myfastrepeat1(:,1) = unique(myfasttotal1(:,1));
myfastrepeattemp = arrayfun(@(x)length(find(myfasttotal1(:,1) == x)), unique(myfasttotal1(:,1)), 'Uniform', false);
myfastrepeat1(:,2) = cell2mat(myfastrepeattemp);
end
So say I have three incidences of stimulus -0.5768 - of those three presentations, the observer got two presentations correct. In my myfasttotal1 file, this would be represented thus:
[-0.5768, 0; -0.5768, 1; -0.5768, 1]
Having got this far, I'm now a bit stuck as to how to tackle creating a new column in myfastrepeat1 which states how many presentations were correct for each unique stimulus. I'm not sure whether I should still be using arrayfun for this or using histc, or indeed going down the indexing route. I figure that provided I can get MATLAB to consider each set of repeated stimulus values as a group, I could then get the count of 1 for each group, so in the above example the count of 1s would be 2, representing the number of correct answers.
Thankyou in advance for any advice you can give, and if you need more elaboration on what I'm trying to do, let me know!
Sean de Wolski on 16 Aug 2012
@Anon, it's slow and confusing and thus has no redeeming values.

Oleg Komarov on 16 Aug 2012
[un,trash,sub] = unique(myfasttotal1(:,1));
count = accumarray(sub,myfasttotal1(:,2));
[un, count]
The last line will display for each stimulus level, the number of successes.
##### 2 CommentsShowHide 1 older comment
Marianne on 16 Aug 2012
Excellent! I did come across accumarray a few times while browsing the questions on here but wasn't sure if it could separate while accumulating. I shall go away and read the help files on it to make sure I understand what's going on with it, and then I'll change my code. Thankyou!

### Categories

Find more on Matrix Indexing in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!