how to initialize a vector of structure

29 Ansichten (letzte 30 Tage)
XAXRXTX
XAXRXTX am 4 Mär. 2014
Kommentiert: Jos (10584) am 4 Mär. 2014
hello
so i have the example abouve
for i = 1 : n
structure.a = .......
structure.b = .......
.
.
structure.z = .......
my_vector(i) = structure;
end
the question is how i can preallocte the space size for the vector my_vector ?
thanks in advance
  1 Kommentar
James Tursa
James Tursa am 4 Mär. 2014
What is the stuff on the right-hand-side? Are you attempting to just get my_vector pre-allocated to hold the correct fields but not actually have anything in the field elements?

Melden Sie sich an, um zu kommentieren.

Melden Sie sich an, um diese Frage zu beantworten.

Antworten (4)

Mischa Kim
Mischa Kim am 4 Mär. 2014
XAXRXTX, check out the documentation.
  1 Kommentar
XAXRXTX
XAXRXTX am 4 Mär. 2014
thanks Mischa Kim
but, but I do not want to initialize every field of the structure !!!

Melden Sie sich an, um zu kommentieren.

Kan-Hua
Kan-Hua am 4 Mär. 2014
To preallocate memory, you need to put some values into the data structure that you are using. I think it's the design of Matlab. For example, to preallocate a memory for a 25x25 matrix, you need
mtx=zeros(25)
or
mtx=ones(25)
It is the same case for a structure array. To preallocate the memory space, you have to put some dummy values into every fields of the structure.
Jos (10584)
Jos (10584) am 4 Mär. 2014
Bearbeitet: Jos (10584) am 4 Mär. 2014
As Mischa pointed out: preallocation of structures is easy:
S(1:5) = struct('a',zeros(10,1),'b','empty')
  2 Kommentare
XAXRXTX
XAXRXTX am 4 Mär. 2014
but , it's tedious to write S = struct('a','empty', 'b','empty', 'c','empty' ,'d','empty'...
................, 'z','empty');
there 's no other solution in fonction of the number of the structure field ???
Jos (10584)
Jos (10584) am 4 Mär. 2014
If your fieldnames are known and you all want to set them to the same default value, in a 1-by-N array of structures S , try this
fn = {'a','b','c','d'} ; % this can be coded as well ...
value = zeros(1,10) ;
N=5 ;
S(1:N) = cell2struct(repmat({value},numel(fn),1),fn,1)

Melden Sie sich an, um zu kommentieren.

Kan-Hua
Kan-Hua am 4 Mär. 2014
You can consider using table instead of structure array to store your data, which gives some flexibility to access the members. However, the version of you Matlab has to be 2013b or later.
Here's some example code of using table, which may solve your problem:
% initialise a table
zarray=zeros(1,3);
T=array2table(zarray,'VariableNames',{'colA','colB','colC'});
%show the initial values of the array
disp(T);
% assign the first row of the table by using names
T.colA(1)=1;
T.colB(1)=2;
T.colC(1)=3;
%Print out the table
disp(T);
% Alternatively, you can do it by index
for i=1:size(T,2)
T(2,i)={i*2};
end
% Print out the table
disp(T)

Kategorien

Mehr zu Data Type Conversion finden Sie in Help Center und File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by