MATLAB Central Newsreader - How can I use plus operator on dataset element?

How can I use plus operator on dataset element?

Richard Johnson — Mon, 09 Nov 2009 10:46:01 -0500

Does anyone know how to use operators such as 'plus' with elements of a datest?

I want to do the following:

A is a dataset of size (m,5).
B=zeros(1,5)

for i =1:m
for j=1:5
     B(1,j)=B(1,j)+A(i,j);
  end;
end;

This generates an error an error message because I can't use the operator 'plus' with an element of a dataset. MATLAB seems to want me to refer to each column in dataset A like this:

for i=1:m
   B(1,1)=B(1,1)+A.Var1(i)
end

But this isn't convenient if I have to perform the same operation on lots of columns.

Is there a way I can use the plus operator on a dataset?

Many thanks,

Richard.

Re: How can I use plus operator on dataset element?

Steven Lord — Mon, 09 Nov 2009 14:23:29 -0500

"Richard Johnson" <Richard.Johnson@fsa.gov.uk> wrote in message
news:hd8rt9$9r6$1@fred.mathworks.com...
> Does anyone know how to use operators such as 'plus' with elements of a
> datest?
>
> I want to do the following:
>
> A is a dataset of size (m,5).
> B=zeros(1,5)
>
> for i =1:m
> for j=1:5
> B(1,j)=B(1,j)+A(i,j);
> end;
> end;
>
> This generates an error an error message because I can't use the operator
> 'plus' with an element of a dataset.

That's correct, PLUS is not defined for dataset objects. What would it mean
to add two dataset objects together if they had different numbers of
observations, different variables, etc? [If that's the type of thing you're
interested in doing, look at the HORZCAT, VERTCAT, CAT, and JOIN methods for
dataset arrays.]

> MATLAB seems to want me to refer to each column in dataset A like this:
>
> for i=1:m
> B(1,1)=B(1,1)+A.Var1(i)
> end
>
> But this isn't convenient if I have to perform the same operation on lots
> of columns.

Use DATASETFUN.

http://www.mathworks.com/access/helpdesk/help/toolbox/stats/dataset.datasetfun.html

> Is there a way I can use the plus operator on a dataset?

See above.

--
Steve Lord
slord@mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ

Re: How can I use plus operator on dataset element?

Richard Johnson — Mon, 09 Nov 2009 14:47:02 -0500

Dear Steve Lord,

thanks for your reply. Sorry, but I don't see how to use the datasetfun function. What am I supposed to substitute for 'fun' in this case? 'Plus' doesn't seem to work.

Maybe it would be easier not to use datasets. I don't think they existed when I first learned MATLB. Can I transform a dataset object A into a matrix B such that MATLAB will not complain about references to B(i,j)?

Many thanks,

Richard.

"Steven Lord" <slord@mathworks.com> wrote in message <hd98j6$8n4$1@fred.mathworks.com>...
>
> "Richard Johnson" <Richard.Johnson@fsa.gov.uk> wrote in message
> news:hd8rt9$9r6$1@fred.mathworks.com...
> > Does anyone know how to use operators such as 'plus' with elements of a
> > datest?
> >
> > I want to do the following:
> >
> > A is a dataset of size (m,5).
> > B=zeros(1,5)
> >
> > for i =1:m
> > for j=1:5
> > B(1,j)=B(1,j)+A(i,j);
> > end;
> > end;
> >
> > This generates an error an error message because I can't use the operator
> > 'plus' with an element of a dataset.
>
> That's correct, PLUS is not defined for dataset objects. What would it mean
> to add two dataset objects together if they had different numbers of
> observations, different variables, etc? [If that's the type of thing you're
> interested in doing, look at the HORZCAT, VERTCAT, CAT, and JOIN methods for
> dataset arrays.]
>
> > MATLAB seems to want me to refer to each column in dataset A like this:
> >
> > for i=1:m
> > B(1,1)=B(1,1)+A.Var1(i)
> > end
> >
> > But this isn't convenient if I have to perform the same operation on lots
> > of columns.
>
> Use DATASETFUN.
>
> http://www.mathworks.com/access/helpdesk/help/toolbox/stats/dataset.datasetfun.html
>
> > Is there a way I can use the plus operator on a dataset?
>
> See above.
>
> --
> Steve Lord
> slord@mathworks.com
> comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
>

Re: How can I use plus operator on dataset element?

Loren Shure — Mon, 09 Nov 2009 20:45:56 -0500

In article <hd9a16$aqi$1@fred.mathworks.com>, Richard.Johnson@fsa.gov.uk
says...
> Dear Steve Lord,
>
> thanks for your reply. Sorry, but I don't see how to use the datasetfun function. What am I supposed to substitute for 'fun' in this case? 'Plus' doesn't seem to work.
>
> Maybe it would be easier not to use datasets. I don't think they existed when I first learned MATLB. Can I transform a dataset object A into a matrix B such that MATLAB will not complain about references to B(i,j)?
>
> Many thanks,
>
> Richard.

You need to supply a function handle (according to the help) so that
would be @plus, not 'plus'

--
Loren
http://blogs.mathworks.com/loren