Set variable in Matlab Dataset array to a single value

Question

Let's say I have a dataset array (from the statistics toolbox):

>> myds
myds = 
    Observation    SheepCount
    1              88        
    2               2        
    3              14        
    4              12        
    5              40

I'm putting together data from various sources, so I'd like to set 'Location' to be 4 in all of these observations, before I vertcat this dataset together with others. In a normal matrix, you'd say myds(:, 3) = 4, which would broadcast the 4 into all of the spaces in the matrix.

Is there a way to do that on a dataset without using repmat?

Things I've tried that don't work:

myds(:, 'Location') = 4
myds(:).Location = 4
myds.Location(:) = 4
myds.Location = 4

Things that work:

myds.Location = 4; myds.Location(:) = 4; % have to run both
myds.Location = repmat(4, length(myds), 1);

~~So, do I have to get over my aversion to repmat? Thanks.~~

edit: I guess what I actually want is to avoid specifying the dimensions of the array of 4's.

abcd · Accepted Answer · 2011-05-09 20:37:43Z

2

You can try using ones instead of repmat.

myds.Location=4*ones(1,5);

answered May 9, 2011 at 20:37

abcd

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2 Comments

rescdsk Over a year ago

Thanks, that's nice, but in anything but a trivial case it'll still have to be 4*ones(length(myds),1), which is still kinda ugly.

abcd Over a year ago

I understand what you're trying to do, but I don't think it can be done with datasets, although it works perfectly fine with arrays. Your first suggestion is perhaps the simplest. Personally, I would say myds.Location=4*ones(size(myds.Observation)) is quite clear to understand, and gets the job done in a line.

Rasman · Accepted Answer · 2011-05-10 03:10:57Z

1

it's not elegant but you can also try:

myds.Location= myds.Observation*0 + 4;

answered May 10, 2011 at 3:10

Rasman

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