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Re: using getfield() with a stuct array
Posted:
Jan 18, 2013 5:14 PM


"Bruce Elliott" <bruce.elliott@jhuapl.nospam.edu> wrote in message news:kdc3h7$d6b$1@newscl01ah.mathworks.com... > Is there any way to use getfield() on an array of structure and to get a > samesized array of field values? > > In other words, I can do this: > > x = [myArr.F]; > > to get an array with the values in the field F in my stuct array, myArr. > > This, however, does not work: > > x = getfield(myArr,'F'); > > (Putting [] around anything on the righthandside does not help.) > > There's probably a good reason for this, but the documentation suggests > that x = getfield(S,'F') is equivalent to x = S.F, so I would have hoped > that I could do this.
For _scalar_ struct arrays S, yes those are equivalent.
http://www.mathworks.com/help/matlab/ref/getfield.html
"value = getfield(struct, 'field'), where struct is a 1by1 structure, returns the contents of the specified field, equivalent to value = struct.field." and "If structure struct or any of the fields is a nonscalar structure, and you do not specify an Indx, the getfield function returns the values associated with the first index."
Try:
thefieldname = 'F'; x = [myArr.(thefieldname)]
You can use this like:
F = struct('x', {2, 5, 17}) z = F(mod([F.('x')], 2) == 1)
This will extract the elements of F whose x fields contain odd values. From the way I constructed F you would expect z to contain two elements, and it does.
 Steve Lord slord@mathworks.com To contact Technical Support use the Contact Us link on http://www.mathworks.com



