Getting all values in the same field for different entries within a structure

조회 수: 15 (최근 30일)
Imagine I have a structure of students with certain info and their grades for different modules, looking like:
student(1).grades.math = 7;
student(2).grades.math = 9;
This student list might be any number. Is it possible to get all the different math grades in an array without a for-loop?
mathGrades = student.grades.math;
This doesn't seem to work and gives me the following error:
"Intermediate dot '.' indexing produced a comma-separated list with 2 values, but it must produce a single value when followed by subsequent indexing operations."

채택된 답변

Vilém Frynta
Vilém Frynta 2023년 4월 21일
편집: Vilém Frynta 2023년 4월 21일
Try arrayfun (use function on the struct to extract the values into the array).
An example on your data:
% Your data
student(1).grades.math = 7;
student(2).grades.math = 9;
student(3).grades.math = 6;
% Use arrayfun to extract all the math grades into vector
mathGrades = arrayfun(@(x) x.grades.math, student)
mathGrades = 1×3
7 9 6
Hope my answer was useful. If it was, I'd be happy if you could accept my answer.

추가 답변 (1개)

Stephen23
Stephen23 2023년 4월 22일
편집: Stephen23 2023년 4월 22일
"Is it possible to get all the different math grades in an array without a for-loop?"
Of course.
The simple and efficient MATLAB approach is to use comma-separated lists:
student(1).grades.math = 7;
student(2).grades.math = 9;
student(3).grades.math = 6;
tmp = [student.grades];
out = [tmp.math]
out = 1×3
7 9 6
Avoid slow ARRAYFUN.

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