Initialization of persistent variable in Matlab

I want to use a persistent variable inside a matlab function block but I can't initialize it. I want to either initialize it from an m.file or do it inside the function.

If I use isempty then the variable is given a size of 1x1 and I don't want that. Basically I don't know how to handle the persistent value as it is taken as 1x1 or as not defined. How can I use isempty but do not give it a 1x1 size? Or how can I initialize it from an m.file?

function y1 = fcn(u)



persistent y;



if isempty(y)

y=0;

end



for i=1:1:length(u)

    if u(1,i) >=10

       y(1,i) = 1;

    elseif u(1,i) <= 5

       y(1,i) = 0;

    else 

        ;

    end

end



y1=y;



end

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

@Jigg,My persistent variable is fixed in size, let's say a vector 1x10. It changes with time since the system is dynamic. I just want it to be set to zeros only once and not every time the function is called. With isempty in the function I get 1x1 and I can't do it through workspace/m.file.
– Engineer
May 27 '14 at 14:43

@Jigg, Of course, since the variable is empty in the beginning it is a way to initialize it. It's also stated in matlab help for that reason. I will update the post with the code.
– Engineer
May 27 '14 at 14:49

As I told you it is a dynamic system, so the initialization is not important. It will run after some time properly whatever these initial conditions are.
– Engineer
May 27 '14 at 14:59

add a comment |

I want to use a persistent variable inside a matlab function block but I can't initialize it. I want to either initialize it from an m.file or do it inside the function.

function y1 = fcn(u)



persistent y;



if isempty(y)

y=0;

end



for i=1:1:length(u)

    if u(1,i) >=10

       y(1,i) = 1;

    elseif u(1,i) <= 5

       y(1,i) = 0;

    else 

        ;

    end

end



y1=y;



end

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

@Jigg,My persistent variable is fixed in size, let's say a vector 1x10. It changes with time since the system is dynamic. I just want it to be set to zeros only once and not every time the function is called. With isempty in the function I get 1x1 and I can't do it through workspace/m.file.
– Engineer
May 27 '14 at 14:43

@Jigg, Of course, since the variable is empty in the beginning it is a way to initialize it. It's also stated in matlab help for that reason. I will update the post with the code.
– Engineer
May 27 '14 at 14:49

As I told you it is a dynamic system, so the initialization is not important. It will run after some time properly whatever these initial conditions are.
– Engineer
May 27 '14 at 14:59

add a comment |

I want to use a persistent variable inside a matlab function block but I can't initialize it. I want to either initialize it from an m.file or do it inside the function.

function y1 = fcn(u)



persistent y;



if isempty(y)

y=0;

end



for i=1:1:length(u)

    if u(1,i) >=10

       y(1,i) = 1;

    elseif u(1,i) <= 5

       y(1,i) = 0;

    else 

        ;

    end

end



y1=y;



end

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

I want to use a persistent variable inside a matlab function block but I can't initialize it. I want to either initialize it from an m.file or do it inside the function.

function y1 = fcn(u)



persistent y;



if isempty(y)

y=0;

end



for i=1:1:length(u)

    if u(1,i) >=10

       y(1,i) = 1;

    elseif u(1,i) <= 5

       y(1,i) = 0;

    else 

        ;

    end

end



y1=y;



end

matlab persistent

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

edited Nov 21 at 3:16

Cœur

17.4k9102143

edited Nov 21 at 3:16

Cœur

17.4k9102143

edited Nov 21 at 3:16

Cœur

17.4k9102143

asked May 27 '14 at 14:35

Engineer

asked May 27 '14 at 14:35

Engineer

asked May 27 '14 at 14:35

Engineer

@Jigg,My persistent variable is fixed in size, let's say a vector 1x10. It changes with time since the system is dynamic. I just want it to be set to zeros only once and not every time the function is called. With isempty in the function I get 1x1 and I can't do it through workspace/m.file.
– Engineer
May 27 '14 at 14:43

@Jigg, Of course, since the variable is empty in the beginning it is a way to initialize it. It's also stated in matlab help for that reason. I will update the post with the code.
– Engineer
May 27 '14 at 14:49

As I told you it is a dynamic system, so the initialization is not important. It will run after some time properly whatever these initial conditions are.
– Engineer
May 27 '14 at 14:59

add a comment |

@Jigg,My persistent variable is fixed in size, let's say a vector 1x10. It changes with time since the system is dynamic. I just want it to be set to zeros only once and not every time the function is called. With isempty in the function I get 1x1 and I can't do it through workspace/m.file.
– Engineer
May 27 '14 at 14:43

@Jigg, Of course, since the variable is empty in the beginning it is a way to initialize it. It's also stated in matlab help for that reason. I will update the post with the code.
– Engineer
May 27 '14 at 14:49

As I told you it is a dynamic system, so the initialization is not important. It will run after some time properly whatever these initial conditions are.
– Engineer
May 27 '14 at 14:59

@Jigg,My persistent variable is fixed in size, let's say a vector 1x10. It changes with time since the system is dynamic. I just want it to be set to zeros only once and not every time the function is called. With isempty in the function I get 1x1 and I can't do it through workspace/m.file.
– Engineer
May 27 '14 at 14:43

@Jigg, Of course, since the variable is empty in the beginning it is a way to initialize it. It's also stated in matlab help for that reason. I will update the post with the code.
– Engineer
May 27 '14 at 14:49

As I told you it is a dynamic system, so the initialization is not important. It will run after some time properly whatever these initial conditions are.
– Engineer
May 27 '14 at 14:59

add a comment |

1 Answer
1

active

oldest

votes

You are initializing y to a scalar. If you want to initialize it to an empty vector of zeros, use y=zeros(1,n) where n is the number of elements you want it to have.

answered May 27 '14 at 15:07

craigim

3,22711435

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

1

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

add a comment |

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1 Answer
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You are initializing y to a scalar. If you want to initialize it to an empty vector of zeros, use y=zeros(1,n) where n is the number of elements you want it to have.

answered May 27 '14 at 15:07

craigim

3,22711435

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

1

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

add a comment |

You are initializing y to a scalar. If you want to initialize it to an empty vector of zeros, use y=zeros(1,n) where n is the number of elements you want it to have.

answered May 27 '14 at 15:07

craigim

3,22711435

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

1

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

add a comment |

You are initializing y to a scalar. If you want to initialize it to an empty vector of zeros, use y=zeros(1,n) where n is the number of elements you want it to have.

answered May 27 '14 at 15:07

craigim

3,22711435

You are initializing y to a scalar. If you want to initialize it to an empty vector of zeros, use y=zeros(1,n) where n is the number of elements you want it to have.

answered May 27 '14 at 15:07

craigim

3,22711435

answered May 27 '14 at 15:07

craigim

3,22711435

answered May 27 '14 at 15:07

craigim

3,22711435

answered May 27 '14 at 15:07

craigim

3,22711435

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

1

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

add a comment |

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

1

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

If I do that IN the function, y will be set to 0 every time the function is called. But I want to keep the values, that's why I have a persistent variable.
– Engineer
May 27 '14 at 15:13

Only if y is empty. isempty returns either true or false. If true, then it initializes to an empty vector. if false, it skips that line and uses the persistent values that are already stored in the variable.
– craigim
May 27 '14 at 15:15

One other thing to pay attention to. The values are persistent as long as MATLAB is running. In order to clear y the first time you run, you should include the command clear fcn before the first call to fcn.
– craigim
May 27 '14 at 15:19

Yes, it finally worked! I thought I had to run through the elements but a check of just y is enough. That's why I couldn't run it, because I was trying to check individual cells. In my case doing it for the whole vector is the same. Thanks a lot!
– Engineer
May 27 '14 at 15:23

Here is some bonus help. The for/end block can be vectorized and completed in just two steps using logical indexing y(u>=10) = 1; y(u<=5) = 0;.
– craigim
May 28 '14 at 3:24

add a comment |

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