how to use find to cell cell indexing

why does this not work ?

find(grnd_truth_cell{:,1} == 6)

I want to find all of grnd_truth_cell whose 1st column at every row == 6 but matlab tell me Error using == Too many input arguments.

[Image Analyst]

If you just type this on the command line

grnd_truth_cell{:,1}

what does it report to the command window? Show us.

[RuiQi]

These are the last few numbers. It goes from 0 to 7480

ans =

          7480

ans =

          7480

ans =

          7480

ans =

          7480

Answer 1

[dpb]

Because as your command line shows,

grnd_truth_cell{:,1}

is a comma-separated list. Enclose it in the [] to make an array that find can operate over--

find([grnd_truth_cell{:,1}]==6)

[RuiQi]

thank you and imageanalyst, i learnt how to handle 'comma-separated lists' today using []

Answer 2

[Image Analyst]

Maybe you can assign it to a column vector first

col1 = grnd_truth_cell{:,1};
whos col1
rowsThatEqual6 = find(col1 == 6); % Braces.

How does that work? Maybe you need to use cell2mat():

col1 = cell2mat(grnd_truth_cell(:, 1)); % Parentheses

If that doesn't work, attach grnd_truth_cell in a .mat file so I can try some things.

save('grnd_truth_cell.mat', 'grnd_truth_cell');

And please read the FAQ on cell arrays: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F