CODEWITHSUNDEEP
matlab
Nefa
Nefa

Reputation: 1

How do I use variables from a table?

I was wondering how can I call a variable within a table that I have created?

For instance, lets say I have a table with these variables:

Width 3 4.5 5 6.7

Length 4.6 5.7 5.7 5.6

Type 1 1 3 4

How do I ask Matlab to retrieve all numbers that are equal to 1 from Type variable? Here's what I am trying to do:

A=[]; %Create empty matrix
for i=1:numel(Type) %for every number within the variable
  if Type(i) == '1'; %if it equals to 1
      A(i)= Type(1) %append to matrix
  end
end

Upvotes: 0

Views: 73

Answers (1)

Marc
Marc

Reputation: 3313

You need use what's called "logical Indexing" - Let's say you have a variable tbl:

>>tbl= [110 1; 120 2; 13  3;140 1]

tbl =

   110     1
   120     2
    13     3
   140     1

We want to get all entries where the second column is == 1. We can create a similar sized array, where there is an entry for each row of tbl, where it's false if ~=1, or true if it's ==:

>>index = tbl(:, 2)==1

index =

     1
     0
     0
     1

Note the use of the : operator - that says "use all elements" - in this case, all rows. Now, you just apply that to tbl itself:

>> crabs = tbl(index, 1)

crabs =

   110
   140

Now, you can make that a one-liner:

>> crabs = tbl(tbl(:, 2)==1, 1)

Upvotes: 2

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