# How do I create a for loop in MATLAB?

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pedro marin el 5 de Mzo. de 2012
Comentada: DGM el 4 de Nov. de 2023
I am completely lost in for loops, I just don't get it. The book and my professor haven't helped much. Where can I get help?
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Abderrahmane Walid AISSANI el 14 de Mayo de 2017
Editada: Walter Roberson el 14 de Mayo de 2017
hi I am trying to create several variables using the for loop
% for k=1:1:10
tab_k = csvread('');
end
in fact the code is wrong but I want to iterate the "k" in the name of the variable but I can't find how to do that .
thank you .
Walter Roberson el 14 de Mayo de 2017

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### Respuesta aceptada

Walter Roberson el 5 de Mzo. de 2012
Editada: MathWorks Support Team el 9 de Nov. de 2018
A basic for loop in MATLAB is often used to assign to or access array elements iteratively. For example, let’s say you have a vector A, and you want to simply display each value one at a time:
A = [3 6 9 4 1];
for i = 1:length(A)
disp(A(i))
end
For more examples using for loops, see:
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Jake Dalrymple el 21 de Sept. de 2022
This is very helpful! How could you display these values in rows of 5 rather than just one value per row?
Walter Roberson el 21 de Sept. de 2022
Editada: Walter Roberson el 21 de Sept. de 2022
A = randi([0 9], 1, 20)
A = 1×20
1 9 5 8 6 2 6 2 2 0 3 2 1 4 7 3 9 7 2 6
%then output in groups of 5 in vectorized form
reshape(A, 5, []).'
ans = 4×5
1 9 5 8 6 2 6 2 2 0 3 2 1 4 7 3 9 7 2 6
%or if you need a for loop
for K = 1 : 5 : numel(A); disp(A(K:K+4)); end
1 9 5 8 6 2 6 2 2 0 3 2 1 4 7 3 9 7 2 6
Matters get more complicated if the number of entries in the array is not a multiple of the number of columns you want to use. For example,
A = randi([0 9], 1, 23)
A = 1×23
9 6 1 5 7 4 8 4 8 4 4 5 8 5 3 6 9 2 1 4 8 9 9
for K = 1 : 5 : numel(A); disp(A(K : min(end,K+4))); end
9 6 1 5 7 4 8 4 8 4 4 5 8 5 3 6 9 2 1 4 8 9 9

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### Más respuestas (8)

Jan el 5 de Mzo. de 2012
You can get help from the documentation of Matlab:
doc for
help for
There you find examples and explanations.
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Meenakshi Bhardwaj el 19 de Jul. de 2018
Thanks so much. Finally, I understood what is for loop.

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Jan Afridi el 29 de Sept. de 2017
For loop repeat itself for a given number of input. The syntax for “For Loop Matlab” is
for variable = expression
Program Statement
end
In the above syntax, the expression has one of the following forms.
Initial value : Final value
for x = 1:10
fprintf('value of x: %d\n', x);
end
Initial value : Step : Final value
for x = 1:2:10
fprintf('value of x: %d\n', x);
end
Value Array
for x = [1 4 6 8 90]
disp(x)
end
To learn more about in detail visit this link For Loop Matlab
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mohamed mohamed el 6 de Feb. de 2021
Editada: Walter Roberson el 31 de Jul. de 2021
for x = 1:10
fprintf('value of x: %d\n', x);
end
value of x: 1 value of x: 2 value of x: 3 value of x: 4 value of x: 5 value of x: 6 value of x: 7 value of x: 8 value of x: 9 value of x: 10
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Narasimman P el 30 de Jul. de 2021
for a=1:10
end
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Ealam Yassin el 17 de Nov. de 2021
no output
Walter Roberson el 17 de Nov. de 2021
The code posted by @Narasimman P is a completely valid for loop, just one that does not do anything inside the loop. All it does is count from 1 to 10 internally. After the loop, two things will have changed:
1. Time will have elapsed, which could be important if you are waiting for something to happen
2. The loop control variable 'a' will have the same value as it was last assigned, so in this case after the loop 'a' will have the double precision value 10 .
disp('before')
before
whos
disp('starting loop')
starting loop
for a=1:10
end
disp('after')
after
whos
Name Size Bytes Class Attributes a 1x1 8 double
So there has been output: the variable a did not exist before, and after the loop it does exist.

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Manan Shah el 8 de Mayo de 2022
Editada: Torsten el 8 de Mayo de 2022
for i = 0:8 ;
a = pow10 (i);
disp a(i);
end
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Walter Roberson el 8 de Mayo de 2022
disp a(i)
would mean the same thing as
disp('a(i)')
You probably want
disp(a(i))
DGM el 4 de Nov. de 2023
Using
disp(a(i))
would necessitate addressing the zeroth and other nonexistent elements of the scalar variable a.
Besides the fact that this is obviously untested nonworking code, I question why what should rightly be a very simple example needs to include undisclosed user-defined functions.

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Iosif el 13 de Nov. de 2022
Editada: Iosif el 13 de Nov. de 2022
D=input ('Βαθος νερου σε m ')
W=input ('Βαρος ανα μοναδα μηκους της γραμμης αγκυρωσης στο νερο σε N/m ')
Hex=input ('εξωτερικη φορτηση σε kn ')
dx=input ('οριζοντια μετατοπιση σε m ')
if dx/D>=0.3 && dx/D<=0.6
else
disp ('Δωσε διαφορετικη τιμη για το dx')
dx=input ('οριζοντια μετατοπιση σε m ')
end
I want to make my programm go to if after else and run that lines again until if line is satisfied
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Walter Roberson el 15 de Nov. de 2022
while ~isnumeric(dx) || ~isscalar(dx) || dx/D<0.3 || dx/D>0.6
disp ('Δωσε διαφορετικη τιμη για το dx')
dx=input ('οριζοντια μετατοπιση σε m ')
end

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Kartick el 11 de En. de 2023
Editada: Kartick el 11 de En. de 2023
There are 4 type of loops: while, for, if and case.
For loop :
Eg: you have your robot whom you wish to give command to walk 100steps. The command will be
for steps=1:100
end
disp(steps)
100
The robot will go 100steps and stop and output will be displayed as 100 after completion.
For loop is used to solve many mathematical problems like factorials etc.
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Walter Roberson el 11 de En. de 2023
Computer Scientists use the term "control statement" for code structures that will execute selectively exactly zero or one time. Computer Scientists use the term "loop" for code structures that have the potential to execute more than one time. "if" and "case" are control structures but are not loops.
If you imagine the execution point as starting from the "top" and falling downward, then "if" and "case" only ever have the execution point continuing to fall downwards, whereas "for" and "while" in general require pumping the execution point back up again.

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Thanh el 4 de Nov. de 2023
I am using matlap 2017b but I no find simulation pacing options . I need some help .
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Walter Roberson el 4 de Nov. de 2023
Introduced in R2018a

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