Accumarray error: First input SUBS must contain positive integer subscripts.

Hello,

The accumarray function is causing me problems - the error is embedded within the question. Attached you find a sample file and below you find the piece of code I wrote:

   temp_raw_JE50=X0012_50(:,20)-X0012_50(:,17); % raw overall JE50
   temp_AO50=ismember(X0012_50(:,13),0); % AO trials (0's) in col. 13 of temp_file_50
   temp_raw_JE50AO= accumarray(temp_raw_JE50,temp_AO50); % raw JE50 for AO trials only

Could you please be so kind as to help me?

Bianca

Answer 1

[Sean de Wolski]

[uval,~,subs] = unique(temp_raw_JE50);
accumarray(subs,vals)

You most likely want to accumulate by the unique values. Since these aren't necessarily positive integer indices, use unique first and pass the indices into accumarray.

[Bianca Elena Ivanof]

Thank you - I've tried your option but the script keeps crashing (new error: 'Second input VAL must be a vector with one element for each row in SUBS, or a scalar.'), partly because I can't understand why you use [uval,~,subs] in the example above, so I may not be using it correctly - I know uval and subs refer to the values that come in brackets after accumarray, but I'm missing the big picture.

Is vals the same with uval?

Moreover, would accumarray(subs,vals) replace the accumarray(temp_raw_JE50,temp_AO50) in my script above or accumarray(subs,vals) comes before ismember and accumarray in my script?

Could you please be so kind as to explain?

Answer 2

[Andrei Bobrov]

[uval,~,subs] = unique(X0012_50(:,20)-X0012_50(:,17));
temp_raw_JE50AO = accumarray(subs,~X0012_50(:,13));
out = [uval, temp_raw_JE50AO];

[Bianca Elena Ivanof]

Thank you. It works. Could you please be so kind as to talk me through code a bit? What I don't understand is:

- what is [uval,~,subs]? a function? the name of a variable? an array? - what is 'out'? what is its function?

Thanks in advance

[Andrei Bobrov]

uval, subs - variable.

out - the calculation result

[Bianca Elena Ivanof]

thank you.

[Sean de Wolski]

Look at the documentation for examples and descriptions of what the pieces are:

doc unique