MATLAB: Variable

variablevariables

Hello, If i have

X=rand(20,1)
Y=rand(20,1)
then i want to do 
p1=[x(1)   y(1)]
p2=[x(2)   y(2)]
.    .      .
.    .      .
.    .      .
p20=[x(20) y(20)]

How can i intialize these p1 to p20 values with the help of loop instead of intiallizing manually?

The varaible needs to be updates as p1…p20.

Finally with structure P has terms p1…p20, with p1…p20 have their values from X and Y

Thanks in advance

Best Answer

variant use cell array

X=rand(20,1)
Y=rand(20,1)
p = mat2cell([X Y],ones(20,1),2)

bad version

for j1 = 1:size(X,1)
   jc = num2str(j1);
   eval(['p' jc '= [X(' jc '), Y(' jc ')]']);
end

So do not ever! Use the better 'p{1}' of the first variant instead of 'p1'

Related Solutions

MATLAB: How to access a structure array using a loop

First, note that with your example, at the end p is a structure with just one field 'p10'. To create the structure you want:

p = struct('p1', {p1}, 'p2', {p2}, 'p3', {p3}, ...)

Also note that you don't need to put the field contents into a cell array, unless this content is itself a cell array. so:

 p = struct('p1', p1, 'p2', p2, ...)

may work just as well.

Secondly, your for loop is not going to work, ['p1' 'p2' 'p3' ...] is exactly the same as 'p1p2p3....', and i will take in turn the values 'p', then '1', then 'p' again, then '2', etc. You need to use a cell array

Finally, to use dynamic field names, you enclose the variable holding the field name in round brackets ().

So:

p = struct('p1',{p1}, 'p2',{p2}, 'p3',{p3}, 'p4',{p4}), 'p5',{p5}, 'p6',{p6}, 'p7',{p7}, 
'p8',{p8}, 'p9',{p9}, 'p10',{p10});
for fn = {'p1', 'p2', 'p3', 'p4', 'p5', 'p6', 'p7', 'p8', 'p9', 'p10'}
%or better: for fn = fieldnames(p)'
   o = p.(fn{1});
end

MATLAB: How to create a structure

YourStruct = struct('A', {cell(20,1)}, 'B', {zeros(20,1)}, 'C', {zeros(20,1)}, 'D', {zeros(20,1)}, 'E', {zeros(20,1)}, 'F', {zeros(20,1)});

Or if you prefer,

YourStruct.A = cell(20,1);
for FN = 'BCDEF'
  YourStruct.(FN) = zeros(20,1);
end

Best Answer

Related Solutions

MATLAB: How to access a structure array using a loop

MATLAB: How to create a structure

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