I understand that you are attempting to create partitions of your datastore and are experiencing difficulties with it. You also observed that the partitions created are empty tables.
Please note that in order to create datastore partitions, the datastore needs to have more than one file. The datastore referred to in the code snippet has only one ‘CSV’ file and thus cannot be partitioned. You can determine the number of partitions in a datastore using the “numpartitions()” function and the syntax for this function is demonstrated below:
X=numpartitions(subds)
You will be able to see that the number of partitions remains '1', both before and after attempting to create partitions because there is only one file in the datastore. This is the reason why any partition accessed after index ‘1’ results in an empty table.
If you would like to perform “row-wise partition” of a file within the datastore, a possible workaround for it would be using the “read” function. After the data is read to a variable, it can be further ‘sliced’, ‘indexed’ and ‘labeled’ as shown below:
ds = tabularTextDatastore(‘airlinesmall.csv’);
temp=ds.read;
%extracting a particular column
subds=temp.Month;
%extract the first out of 3 partitions
subds=temp(height(temp)/3, : );
Please refer to the following MathWorks documentation links for more information on “DataStore” and “Indexing”:
- https://www.mathworks.com/help/matlab/import_export/what-is-a-datastore.html
- https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html
Hope this helps.
