Comparing Dataset

Hi everyone,

I'm a newbie in matlab.

I have two big datasets with different number of row but same number in column. I need to compare each element of both datasets with reference of column #1. If column #1 in both data set has exactly the same value then subtract column 2 in 1st dataset with 2nd dataset.

Let says:

dataset1 = [1 2; 2 2; 3 5; 4 2; 5 10]; dataset2 = [1 4; 3 2; 5 2];

and the result that I want is:

result = [1 -2; 3 3; 5 8]

How can I solve this? Thanks in advance.

Answer 1

[Walter Roberson]

Use the three-output version of ismember to figure out which columns match which.

[Mr D]

Hi Walter,

Thanks for fast reply..Yes, I can define the correlation between two dataset, but when I try to do the operation between these datasets, it doesn't give me the result what I want.

Here my if statement:

dataset1 = [1 2; 2 2; 3 5; 4 2; 5 10];

dataset2 = [1 4; 3 2; 5 2];

is_mem = ismember(dataset1(:,1),dataset2(:,1));

delta = zeros(size(dataset1(:,1)));

for i =1:size(dataset1)

if (is_mem(i,1) == 1);

delta(i,1) = dataset1 (i,2) - dataset2 (i,2);

end

end

Could you give me a suggestion about this?

Thanks

[Walter Roberson]

You only used the single-output version of ismember(). Please read the documentation for ismember() and look at the additional outputs that are available.

[Mr D]

I modified my code,

dataset1 = [1 2; 2 2; 3 5; 4 2; 5 10];

dataset2 = [1 4; 3 2; 5 2];

[is_mem,loc] = ismember(dataset2(:,1),dataset1(:,1));

delta = zeros(size(dataset2(:,1)));

for i = 1:size(dataset2)

for j= 1: size(dataset1)

if (loc(i,1) ~= 0);

delta(i,1) = dataset1 (j,2) - dataset2 (i,2);

end

end

end

and the result is still not what I want.

delta = [6;8;8]

the delta what I want is [-2,3,8].

What's wrong with my code?I'm really newbie in coding, could you give me more clear solution?

Thanks.

[Mr D]

Hi Walter,

Finally I can get the result what I want in simple code:

dataset1 = [1 2; 2 2; 3 5; 4 2; 5 10];

dataset2 = [1 4; 3 2; 5 2];

[is_mem,loc] = ismember(dataset2(:,1),dataset1(:,1));

v = dataset1(loc,2);

delta = dataset1(loc,2) - dataset2(:,2);

Thanks