Delete row from a structure array

For some reason, the solutions given on the internet don't seem to work for me. The most common solution I have seen is to just do what one would do for arrays. If 'a' is a structure array and I want to delete the 9th entry from all fields:

a(9)=[];

I get an error message saying "Matrix index is out of range for deletion."

What am I doing wrong? My strucutre array has both numeric and cell arrays. I tried removing the cell array field entirely and trying the above operation on the new array (which has only numeric fields), that didn't work either.

Thanks.

Answer 1

[Matt J]

As far as can be seen, you simply aren't correctly assessing the number of elements in a. When a has 9 elements or more, as in the following example, things should work

    >> clear a
    >> a(20).numeric=123; a(20).cell={'dog','cat'}

          a = 

          1x20 struct array with fields:

              numeric
              cell

    >> a(9)=[]

          a = 

          1x19 struct array with fields:

              numeric
              cell

[bertie]

Thanks, you are right. Turns out my I have a struct variable (ASSET) that is not an array but has fields that are arrays. What I mean is the size of ASSET is 1x1 but I can access individual entries using ASSET.id(9), say.

ASSET =

       id: [1x53369 double]
    dtnum: [1x53369 double]
      lat: [1x53369 double]
      lon: [1x53369 double]
     type: {1x53369 cell}
      sst: [1x53369 double]
      sss: [1x53369 double]

I guess the solution is to delete the rows by accessing each individual field:

ASSET.id(rows to delete)=[] ;
ASSET.dtnum(rows to delete)=[] 
. 
. and so on.

Not the most elegant way to do things but will work.

[Walter Roberson]

You might want to consider putting all of the numeric information together into one array, 6 x 53369 double, and accessing by rows when using the data. For example,

as_id = 1;
as_dtnum = 2;
as_lat = 3;
as_lon = 4;
as_sst = 5;
as_sss = 6;

ASSET.data(as_id,431)  %equivalent to old ASSET.id(431)

and then you can delete all of the information for one asset by

ASSET.data(:,9) = [];
ASSET.type(9) = [];

(the cell needs to be maintained separately from the numeric values if you want easy numeric access to the numeric data.)