Can I perform subtraction using cell arrays?

Hi all,

I have 2 sets of numbers which i would like to subtract them and compare their values and perform a counter loop.

Is there any function I can make use of to do that? Thanks

for example I have these 2 sets of numbers which I need to subtract each value and compare:

filteredAreaSample =

        3594        3627        3626        3625        3610

filteredAreaStudent =

        3648        3621        3613        3620        3626

[Matt J]

It really doesn't make sense for you to maintain data like this in cell arrays. Data like this can be held in simple matrices, making them very simple (and CPU optimized) to subtract

 Differences = filteredAreaSample - filteredAreaStudent

Cell arrays are meant mainly for situations where you have arrays of different sizes or types, e.g.,

mycell={rand(5), eye(3),'dog','cat'},

or when you want to perform comma-separated list operations, e.g.,

[A,B,C,D]=deal(mycell{:});

Answer 1

[Azzi Abdelmalek]

A ={  3594  3627   3626  3625   3610}
B ={  3648   3621  3613  3620   3626}
res=cellfun(@(x,y) y-x,A,B)

[Yao]

Hi Sir,

I got this error "Function name must be a string."

How do I troubleshoot it?

[Azzi Abdelmalek]

did you copy and past the code?, if not, what did you do? or show us a sample of your data

[Yao]

Hi Sir,

This is my code:

>> Sample1 = imread('Sample1.jpg'); >> Sample1 = img_preprocess_sample(Sample1);

filteredAreaSample =

        3594        3627        3626        3625        3610

>> Student1 = imread('Student1.jpg'); >> Student1 = img_preprocess_student(Student1);

filteredAreaStudent =

        3648        3621        3613        3620        3626

>> filterAreaSample = {3594 3627 3626 3625 3610};

>> filterAreaStudent = {3648 3621 3613 3620 3626};

>> Difference = cellfun(@(x,y) y-x,filterAreaSample,filterAreaStudent)

[Azzi Abdelmalek]

It's wierd, I tested your code, it works. Now to find what is the problem try:

filterAreaSample = {3594 3627 3626 3625 3610};
filterAreaStudent = {3648 3621 3613 3620 3626};
Difference=cell2mat(filterAreaStudent)-cell2mat(filterAreaSample )

what did you get?

[Yao]

Hi Sir, thanks for your help, I got the results.

Just to check, I need to convert the values into a matrix before I can find the difference?

Because for my next step I will need to compare the difference and I was told to convert it to a cell array to compare in a loop

Here is a sample of my code:

I have values stored from DiffQ1 to DiffQ20 I need to compare the values

Difference = 600

Results = 0

if DiffQ1 > Difference

   Results =  Results + 0
else 
   Results = Results + 1
end;

to

if DiffQ20 > Difference

   Results =  Results + 0
else 
   Results = Results + 1
end

[Azzi Abdelmalek]

Yao , what are the sizes of DiffQ1, ...? can you post your full code?

[Yao]

Hi Sir, based on the earlier code, I got the results as shown in the code below. Now I will need to store the results into DiffQ1 to DiffQ20 and compare them with MaxDiff. I will need to compare them 20 times and get the final show the final results.

Difference = cell2mat(filteredAreaStudent) - cell2mat(filteredAreaSample)

Difference =

Columns 1 through 12 

    54    -6   -13    -5    16   -23     9    46   -36    33    65     5

Columns 13 through 20 

   -40    72    45    -8   -49   -31   -15    -8
DifffQ1 = 54;
DiffQ2 = -6;
DiffQ3 = -13;
DiffQ4 = -5;
DiffQ5 = 16;
DiffQ6 = -23;
DiffQ7 = 9;
DiffQ8 = 46;
DiffQ9 = -36;
DiffQ10 = 33;
DiffQ11 = 65;
DiffQ12 = 5;
DiffQ13 = -40;
DiffQ14 = 72;
DiffQ15 = 45;
DiffQ16 = -8;
DiffQ17 = -49;
DiffQ18 = -31;
DiffQ19 = -15;
DiffQ20 = -8;

MaxDifference = 100

Results = 0

if DiffQ1 > Difference

   Results =  Results + 0
else 
   Results = Results + 1
end;

[Azzi Abdelmalek]

you don't need to do it for each value!

res=[ 54  -6 -13 -5 16 -23  9  46 -36 33 65  5 -40  72 45 -8 -49 -31 -15  -8]
out=res>MaxDifference

[Yao]

Hi sir, i tried your method and it works.

Thank you so much for your help.

Lets say if I want to build a counter that says if res is larger then 100; add 1 if res is smaller then 100 add 0, how should I do it? In this case, the output are all zeros, so I should show my results as 20. Thanks again for your help

out = Difference >100

out =

Columns 1 through 12 

     0     0     0     0     0     0     0     0     0     0     0     0

Columns 13 through 20 

     0     0     0     0     0     0     0     0

[Azzi Abdelmalek]

Can you be more clear, you have your array Difference, what test do you want to do? And I think you should accept the answer that correspond to your expectation then post another question.

Answer 2

[Wayne King]

   out = cellfun(@minus,filteredAreaSample,filteredAreaStudent);

[Yao]

Hi Sir,

I got this error "Function name must be a string."