how to get the specific member data from a struct array?

for example,

b=struct('name','JPEG','age','18') ;
c=repmat(b,3,1) ;
d=c.name;
c.name

why is the result of "c.name" different from the result of "d=c.name"?

how to get the member data directly from a struct array or matrix? such as c.name?

and another question, how to create a struct array or matrix directly just like zeros(2,3), but struct(2,3) doesn't work, so how?

Answer 1

[George]

From the doc on struct

"When you access a field of a nonscalar structure, such as s.f, MATLAB® returns a comma-separated list. In this case, s.f is equivalent to s(1).f, s(2).f, s(3).f."

So your d = c.name is equivalent to

d = c(1).name, c(2).name, c(3).name.

Try

[d,e,f] = c.name

to see the difference. See here for more info on how to access data in a struct.

struct(2,3) doesn't work because it's trying to create a 1x1 struct array with field:2 and value:3. Field needs to be a char array.

[xiao]

thank you! inspired by you, i try d = [c(1).name, c(2).name, c(3).name] and

d=[c.name] for a large struct to put the result together, but need to redivide

the result array. so maybe for loop is required.

and to create a struct matrix, maybe the for loop method or repmat way is needed.

Answer 2

[Alexandra Harkai]

What c is is what is called a nonscalar struct array. Then "You cannot assign the list to a single variable with the syntax v = s.f because the fields can contain different types of data." as per the Documentation, so variable d gets only c(1).name, and hence they will be different.

[xiao]

thx! so, for loop method is required to get the data of a struct array or matrix?

[Alexandra Harkai]

Please do not change your question once it has been answered, it is preferred to start new one.