Effacer les filtres
Effacer les filtres

Help when trying to exclude matrix values while indexing!

10 vues (au cours des 30 derniers jours)
SKYLAR SCHUTTER
SKYLAR SCHUTTER le 10 Mar 2020
Commenté : SKYLAR SCHUTTER le 10 Mar 2020
I am trying to figure out how to index a matrix but exclude certain values. Specifically I have
y=grid.y;
latitudes = [-90 90];
I=find(y>=min(lat) & y<=max(lat));
II=find(y<=min(lat) & y>=max(lat));
The first find works (I), the second (II) does not and returns a NaN value. help?
  1 commentaire
Ameer Hamza
Ameer Hamza le 10 Mar 2020
Can you attach a sample dataset so we can try to replicate the issue?

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Réponses (1)

Guillaume
Guillaume le 10 Mar 2020
"the second (II) does not and returns a NaN value"
Firstly, find never returns NaN. It can return an empty array, this is not the same thing at all as NaN.
I wouldn't be surprised that your second expression returns an empty array. numbers that are both smaller than a minimum while at the same time being larger than a maximum are ... very rare! You 2nd expression can be rewritten as:
II = find(y <= -90 & y >= 90);
which clearly is not going to be satisfied often.
In fact, only NaN numbers can satisfy this expression. So your find will return the indices of the NaN values in y or empty if there are no NaN.
  1 commentaire
SKYLAR SCHUTTER
SKYLAR SCHUTTER le 10 Mar 2020
Thank you for your comment! I think my confusion comes from misunderstanding the fundamentals of the "find" function. I was trying to use it to generate an index that represented the columns of my matrix but I see know that that was flawed. Thank you for your help!

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