horzcat
(Not Recommended) Horizontal concatenation for dataset arrays
The dataset data type is not recommended. To work with heterogeneous data,
        use the MATLAB®
        table data type instead. See MATLAB
        table documentation for more information.
Syntax
ds = horzcat(ds1, ds2, ...)
Description
ds = horzcat(ds1, ds2, ...) horizontally concatenates the dataset
   arrays ds1, ds2, ... . You may concatenate dataset arrays that have duplicate
   variable names, however, the variables must contain identical data, and
    horzcat includes only one copy of the variable in the output dataset.
Observation names for all dataset arrays that have them must be identical except for order.
    horzcat concatenates by matching observation names when present, or by
   position for datasets that do not have observation names.