General indexing into structure

Hi, i'm new to working with structures and couldn't seem to find the answer in the documentation. I'm trying to index into a structure to pull out values of one field that have a specific value in another. What I initially tried was structure(structure.field1 == 'string').field2. So what I want is all the values of field 2 that have a specific string in field 1. Any pointers would be appreciated. Also would like advice on how to explain this a bit better, as I realize this might be subpar.

Answer 1

[Voss]

One way to do that is:

structure.field2(strcmp(structure.field1,'string'))

because you want to index into field2, not index into the structure itself, if I understand correctly.

There are other ways to do it, depending on whether the fields of the structure contain string arrays or cell arrays of character vectors.

Example 1, string arrays:

% fields contain string arrays
structure = struct('field1',["here" "are" "some" "strings"],'field2',["and" "some" "other" "strings"])

structure = struct with fields:
    field1: ["here"    "are"    "some"    "strings"]
    field2: ["and"    "some"    "other"    "strings"]

% the syntax suggested above works:
structure.field2(strcmp(structure.field1,'some'))

ans = "other"

% so does this:
structure.field2(strcmp(structure.field1,"some"))

ans = "other"

% so does this:
structure.field2(structure.field1 == "some")

ans = "other"

% so does this:
structure.field2(structure.field1 == 'some') % similar to what you had

ans = "other"

Example 2, cell arrays of character vectors:

% fields contain cell arrays of character vectors
structure = struct('field1',{{'here' 'are' 'some' 'character' 'vectors'}},'field2',{{'and' 'some' 'other' 'character' 'vectors'}})

structure = struct with fields:
    field1: {'here'  'are'  'some'  'character'  'vectors'}
    field2: {'and'  'some'  'other'  'character'  'vectors'}

% the syntax suggested above works:
structure.field2(strcmp(structure.field1,'some'))

ans = 1×1 cell array
    {'other'}

% so does this:
structure.field2(strcmp(structure.field1,"some"))

ans = 1×1 cell array
    {'other'}

% so does this:
structure.field2(structure.field1 == "some")

ans = 1×1 cell array
    {'other'}

% but this gives an error:
structure.field2(structure.field1 == 'some') % similar to what you had

Operator '==' is not supported for operands of type 'cell'.