MATLAB: How to use “netcdf.getVar” to read a part of a variable

.nccountgetvarinqvaridMATLABncidnetcdfstart

I have an NC file with a large matrix in it. I would like to read only a portion of that matrix into memory for my calculation. How can I do this?

Best Answer

First, the best way to easily improve efficiency in NETCDF I/O operations is to use the low level library in MATLAB. You can find documentation on that here:
https://www.mathworks.com/help/releases/R2017b/matlab/ref/netcdf.html
Essentially, the system works as described in the attached "exampleNETCDF.m" file.
In order to read a portion of the variable, you need to
1. open the file
2. get the variable ID
3. use "netcdf.getVar" with the appropriate starting row/column and number of rows/columns
4. close the file
The syntax for "netcdf.getVar" is as such:
>> data = netcdf.getVar(ncid,varid,start,count)
start = [startRow-1, startCol-1]
because MATLAB is 1-indexed and NETCDF is 0-indexed.
count = [numRows, numCols]
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