Loop to open netcdf file and read variables matlab

Question

i want to optimize my code, and I would like to get a loop for my netcdf files. These are the files I want to open and the variables I want to use:

hydrofile2 = 'C:\modelana\netcdf_2019\westcoms2_20190402_0002.nc';
hydrofile3 = 'C:\modelana\netcdf_2019\westcoms2_20190403_0003.nc';
hydrofile4 = 'C:\modelana\netcdf_2019\westcoms2_20190404_0004.nc';
hydrofile5 = 'C:\modelana\netcdf_2019\westcoms2_20190405_0005.nc';
hydrofile6 = 'C:\modelana\netcdf_2019\westcoms2_20190406_0006.nc';
hydrofile7 = 'C:\modelana\netcdf_2019\westcoms2_20190407_0007.nc';
hydrofile8 = 'C:\modelana\netcdf_2019\westcoms2_20190408_0008.nc';
hydrofile9 = 'C:\modelana\netcdf_2019\westcoms2_20190409_0009.nc';
hydrofile10 = 'C:\modelana\netcdf_2019\westcoms2_20190410_0010.nc';
hydrofile11 = 'C:\modelana\netcdf_2019\westcoms2_20190411_0011.nc';
hydrofile12 = 'C:\modelana\netcdf_2019\westcoms2_20190412_0012.nc';
hydrofile13 = 'C:\modelana\netcdf_2019\westcoms2_20190413_0013.nc';
hydrofile14 = 'C:\modelana\netcdf_2019\westcoms2_20190414_0014.nc';
hydrofile15 = 'C:\modelana\netcdf_2019\westcoms2_20190415_0015.nc';

%velocity
u2 = ncread(hydrofile2,'u');
u3 = ncread(hydrofile3,'u');
u4 = ncread(hydrofile4,'u');
u5 = ncread(hydrofile5,'u');
u6 = ncread(hydrofile6,'u');
u7 = ncread(hydrofile7,'u');
u8 = ncread(hydrofile8,'u');
u9 = ncread(hydrofile9,'u');
u10 = ncread(hydrofile10,'u');
u11 = ncread(hydrofile11,'u');
u12 = ncread(hydrofile12,'u');
u13 = ncread(hydrofile13,'u');
u14 = ncread(hydrofile14,'u');
u15 = ncread(hydrofile15,'u');
%salinity
s2 = ncread(hydrofile2,'salinity');
s3 = ncread(hydrofile3,'salinity');
s4 = ncread(hydrofile4,'salinity');
s5 = ncread(hydrofile5,'salinity');
s6 = ncread(hydrofile6,'salinity');
s7 = ncread(hydrofile7,'salinity');
s8 = ncread(hydrofile8,'salinity');
s9 = ncread(hydrofile9,'salinity');
s10 = ncread(hydrofile10,'salinity');
s11 = ncread(hydrofile11,'salinity');
s12 = ncread(hydrofile12,'salinity');
s13 = ncread(hydrofile13,'salinity');
s14 = ncread(hydrofile14,'salinity');
s15 = ncread(hydrofile15,'salinity');
%temperature
t2 = ncread(hydrofile2,'temp');
t3 = ncread(hydrofile3,'temp');
t4 = ncread(hydrofile4,'temp');
t5 = ncread(hydrofile5,'temp');
t6 = ncread(hydrofile6,'temp');
t7 = ncread(hydrofile7,'temp');
t8 = ncread(hydrofile8,'temp');
t9 = ncread(hydrofile9,'temp');
t10 = ncread(hydrofile10,'temp');
t11 = ncread(hydrofile11,'temp');
t12 = ncread(hydrofile12,'temp');
t13 = ncread(hydrofile13,'temp');
t14 = ncread(hydrofile14,'temp');
t15 = ncread(hydrofile15,'temp');

So far, I've just been able to do this:

%% add hydrofiles
clear
myFolder = ('C:\modelana\netcdf_2019\');
if ~isfolder(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end

for k = 1:14
    ncFilename  = sprintf('westcoms2_20190402_0002.nc',k);
if isempty(ncFilename == 1)
    continue; 
else 

ncfile=([myFolder ncFilename]);
s = ncread(ncfile,'salinity') ;
t = ncread(ncfile,'temp') ;
u=ncread(ncfile,'u');
end
end

So I just get one .nc file open with its corresponding variables. But what I want is to be able to get all the files and the variables by using the loop. Thanks and apologize for this basic question

Don't create variable `t1, t2, t3, ... t12`. As I mentioned to you last time, this is called dynamic variable naming and is **bad, very bad, very very much worst**. See [this answer of mine](https://stackoverflow.com/a/32467170/5211833) and references therein. Instead, create **one, single** cell or struct file with the files (e.g. using `dir()` as Ander's answer suggests) then loop over that and make a (N-D) matrix for your other variables. — Adriaan, Jun 09 '20 at 10:36

Ander Biguri · Accepted Answer · 2020-06-09T10:44:53.560

You almost have it, you are missing basic string concatenation/file reading.

You can concatenate strings as [str1, str2, 'random charaters']. e.g. you can do

['westcoms2_2019040', num2str(k), '_000', num2str(k) ,'.nc']

This you can do if you have obvious file formats and some constrains. If you want to read all of them, you can do

fileList = dir([myFolder '*.nc']);

To just get all files with that extension.

Also, remember to store variables independently. i.e.

t(k,:) = ncread(ncfile,'temp') ; % if it is an array
t{k} = ncread(ncfile,'temp') ; % if it is some complex structure

Loop to open netcdf file and read variables matlab

1 Answers1