Using Conditions from One Array To Select Data from Another

I have an array that stores generated hurricane data for hundreds of years with column 1 as the year, column 2 as the latitude, and column 3 as the longitude. I have another array that has a specific selection of years that I want to pull the data from e.g. 857, 865, 890, etc. How do I set up the code to do that? I have tried quite a few different ways and I am always getting the "Arrays have incompatible sizes for this operation." error.

idx=find(comyearlatlong==year_weak_elnino)

I have tried looking into the documentation but I'm just not understanding it well enough to brute force it. I've attached the two files I'm using.

Answer 1

[Voss]

load comyearlatlong.mat
load year_weak_elnino.mat
whos *year*

  Name                       Size              Bytes  Class     Attributes

  comyearlatlong        115600x3             2774400  double              
  year_weak_elnino         149x1                1192  double              

[ism,idx] = ismember(comyearlatlong(:,1),year_weak_elnino);
whos i*

  Name           Size             Bytes  Class      Attributes

  idx       115600x1             924800  double               
  ism       115600x1             115600  logical              

ism is a 115600x1 logical vector saying whether each year in comyearlatlong(:,1) is in year_weak_elnino.

idx is a 115600x1 vector of indices - the location where each element of comyearlatlong(:,1) appears in year_weak_elnino, or 0 if that element of comyearlatlong(:,1) does not appear in year_weak_elnino.

Reference: ismember

[Andrew]

So now that idx indicates yes/no if the years in comyearlatlong are in year_weak_elnino, how do you then pull those years along with the lat/long coordinates into a separate array?

Sorry for all the questions, I'm pretty fresh to MATLAB and am still trying to get the hang of a lot of the basics.

[Voss]

No problem. Here's how you do it:

% ism is the yes/no (you may not actually need idx)
[ism,idx] = ismember(comyearlatlong(:,1),year_weak_elnino);

% get the year/lat/long data for el-nino years:
elnino_data = comyearlatlong(ism,:)