strings comparison with if then in array

Dear all,

Although I've already found a couple of posts on digits and strings together in cell arrays, I couldn't figure out how to explain my issue here.

I have a cell array alpha:

alpha = 383 x 8 cell

column 7 has strings ('miss' or 'incorrect'), the rest has integers.

I simply want to change the value in column 1 every time the correspondent value in column 7 has the label 'miss':

for x=1:383;
if alpha{x,7} == 'miss' | alpha{x,2} == 11; alpha{x,1} = 33; end
if ...
if ...
end

The error I get is:

??? Error using ==> eq MAtrix dimensions must agree

Is it referring to the fact that eq doesn't work for strings? I'm not so sure, because when I remove the for loop, and give a unique value to the x variable, then command works. Also, when I use the for loop, the x value in the Workspace shows the value 1, and not the requested 383. So I guess it is in the way I'm organizing the {} brackets.

I guess it's something silly I cannot see!

Any suggestions would be highly appreciated.

Sincerely,

Udiubu

Answer 1

[Conrad]

Hi Udiubu, you can use strcmp:

strcmp(alpha(x,7),'miss')

You can also get rid of the for loop by using logical indexing; your first test will be

strcmp(alpha(:,7),'miss')|cell2mat(alpha(:,2))==11

so the for loop is replaced by

alpha(logical(strcmp(alpha(:,7),'miss')|cell2mat(alpha(:,2))==11),1) = {33};

[Ubu]

See my comment below

[Jan]

And to explain the problem explicitly: alpha{x,7} == 'miss' compares a [1 x N] char vector with a [1 x 4] char vector. When the contents of alpha{x,7} does not have 1 or 4 characters, the comparison must fail. As Conrad has said already: Compare strings by strcmp.

[Ubu]

The issue is solved by using & instead of |

alpha(logical(strcmp(alpha(:,7),'miss') & cell2mat(alpha(:,2))==11),1) = {33};

[Ubu]

Thanks to both of you! Real precious help.

Sincerely,

Udiubu

[Jan]

There is no need to cast the logical output of STRCMP to a logical.

Answer 2

[Ubu]

Hi Conrad,

This is "almost" great!

As you can see for my previous post - I forgot to mention it in words - is that two conditions have to be meet on order to substitute thr value in column 1:

conditions are:

- I have a 'miss' in column 7 - I have the value 11 in column 2

Your last command seems to do so, it finds the "miss" values and subsitute the value in column 1, but regardless of the value in column 2 (the 11 value).

Is it correct to use "|" to satisfy both commands? Here the second condition in the if loop doensn't work.

Any additional hint would be great.

Now I also understood how logical works!

Thanks!

Udiubu