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Thread Subject:
embedded matlab function error

Subject: embedded matlab function error

From: Mridula

Date: 31 Mar, 2011 10:23:04

Message: 1 of 5

Hi all,
this is a small part of my code in embedded matlab function.

eml.extrinsic('padarray');
envpf=padarray(envp,[fsiz],0,'post');

cfft=fft(envpf);

nfft=length(cfft);



mg_fi_wav=abs(cfft);
fr_fi_wav=(0:nfft/2-1)*(fs/nfft);
 But by running this iam getting an error like this..........

Expected either a logical, char, int, fi, single, or double. Found a MATLAB type. MATLAB types are returned from calls to the MATLAB interpreter and are not supported inside expressions. They may be used on the right-hand side of assignments and as arguments to MATLAB calls.

Function 'Embedded MATLAB Function1' (#56.423.429), line 27, column 14:
"nfft/2"

nfft is already an integer........then y is it showing the error......pls help

Subject: embedded matlab function error

From: wahyoe Unggul

Date: 31 Mar, 2011 12:38:06

Message: 2 of 5

"Mridula" wrote in message <in1km8$aoh$1@fred.mathworks.com>...
> Hi all,
> this is a small part of my code in embedded matlab function.
>
> eml.extrinsic('padarray');
> envpf=padarray(envp,[fsiz],0,'post');
>
> cfft=fft(envpf);
>
> nfft=length(cfft);
>
>
>
> mg_fi_wav=abs(cfft);
> fr_fi_wav=(0:nfft/2-1)*(fs/nfft);
> But by running this iam getting an error like this..........
>
> Expected either a logical, char, int, fi, single, or double. Found a MATLAB type. MATLAB types are returned from calls to the MATLAB interpreter and are not supported inside expressions. They may be used on the right-hand side of assignments and as arguments to MATLAB calls.

form whether "envp", variable or function?
>
> Function 'Embedded MATLAB Function1' (#56.423.429), line 27, column 14:
> "nfft/2"
>
> nfft is already an integer........then y is it showing the error......pls help

Subject: embedded matlab function error

From: Steven_Lord

Date: 31 Mar, 2011 13:30:51

Message: 3 of 5



"Mridula " <mridula.reghu@gmail.com> wrote in message
news:in1km8$aoh$1@fred.mathworks.com...
> Hi all,
> this is a small part of my code in embedded matlab function.
>
> eml.extrinsic('padarray');
> envpf=padarray(envp,[fsiz],0,'post');
>
> cfft=fft(envpf);
>
> nfft=length(cfft);
>
>
>
> mg_fi_wav=abs(cfft);
> fr_fi_wav=(0:nfft/2-1)*(fs/nfft);
> But by running this iam getting an error like this..........
>
> Expected either a logical, char, int, fi, single, or double. Found a
> MATLAB type. MATLAB types are returned from calls to the MATLAB
> interpreter and are not supported inside expressions. They may be used on
> the right-hand side of assignments and as arguments to MATLAB calls.
>
> Function 'Embedded MATLAB Function1' (#56.423.429), line 27, column 14:
> "nfft/2"
>
> nfft is already an integer........then y is it showing the error......pls
> help

Impossible to say, as none of the lines of code you posted compute nfft/2.
Post to the newsgroup (please do NOT email me directly) lines 22-32 of your
code (so that we can see line 27 in context) and someone may be able to
offer some suggestions.

--
Steve Lord
slord@mathworks.com
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

Subject: embedded matlab function error

From: Mike Hosea

Date: 4 Apr, 2011 17:52:59

Message: 4 of 5

The problem here is the use of an extrinsic function. If you don't tell
the compiler the type of what is coming back from an extrinsic function
it remains a "MATLAB type", also known as an mxArray. Very little can
be done with an mxArray in an Embedded MATLAB function other than pass
it to another extrinsic function. Here, because envpf was an mxArray,
the compiler automatically made FFT extrinsic, which made cfft an
mxArray, and so it made LENGTH extrinsic, which made nfft an mxArray,
which you then tried to use in an expression, which isn't supported.

First of all, I don't know what your PADARRAY function does, but the
name is suggestive that you are padding the array with zeros. I hope
you are aware that FFT(X,N) will pad X with zeros if the dimension along
which you are doing the transform has length less than N.

Secondly, the proper way to make an extrinsic call without getting a
MATLAB type back is to pre-declare the output. You need to know the
size and type of the output from the extrinsic function. For example,
you might write

   envpf = complex(zeros(sz));
   envpf = padarray(envp,[fsiz],0,'post');

This looks like the first assignment doesn't do anything, and it doesn't
"do" anything per se, but it tells the compiler to get the mxArray
coming back from padarray and convert it to a complex array of class
'double' with size sz. (Obviously if envp isn't complex, then leave
that part off). Then the subsequent call to FFT won't be made
extrinsic, neither LENGTH to follow, and so the problem should be averted.

BTW, as an aside, you might want to keep the mxArray for the output of
PADARRAY and use the above trick to make the compiler convert the output
of FFT. This is because MATLAB uses FFTW to compute FFT's, and FFTW is
usually faster than the simple radix-2 FFT code generated by the
compiler. FFTW also supports non-power-of-2 lengths, which the simple
radix-2 code does not.
--
Mike

Mridula wrote:
> Hi all,
> this is a small part of my code in embedded matlab function.
>
> eml.extrinsic('padarray');
> envpf=padarray(envp,[fsiz],0,'post');
>
> cfft=fft(envpf);
>
> nfft=length(cfft);
>
>
>
> mg_fi_wav=abs(cfft);
> fr_fi_wav=(0:nfft/2-1)*(fs/nfft);
> But by running this iam getting an error like this..........
>
> Expected either a logical, char, int, fi, single, or double. Found a
> MATLAB type. MATLAB types are returned from calls to the MATLAB
> interpreter and are not supported inside expressions. They may be used
> on the right-hand side of assignments and as arguments to MATLAB calls.
>
> Function 'Embedded MATLAB Function1' (#56.423.429), line 27, column 14:
> "nfft/2"
>
> nfft is already an integer........then y is it showing the
> error......pls help

Subject: embedded matlab function error

From: Mike Hosea

Date: 5 Apr, 2011 17:56:36

Message: 5 of 5

Mike Hosea wrote:
> First of all, I don't know what your PADARRAY function does, but the
> name is suggestive that you are padding the array with zeros. I hope you
> are aware that FFT(X,N) will pad X with zeros if the dimension along
> which you are doing the transform has length less than N.

I just realized that PADARRAY is an Image Toolbox Function, and so I do
know what it does, though I don't know what the variable fsiz is.
--
Mike

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