expvar, impvar (Frequency Domain Identification Toolbox)

Read/write ELiS variance vectors and/or ELiS variance files.

vvect = expvar(varx,vary)
vvect = expvar(varx,vary,covxy,filename,comments,fdate,Ffile)
[varx,vary] = impvar(vdat)
[varx,vary,covxy,comments,fdate] = impvar(vdat)

Description

expvar writes variance data to variance vectors or files.

The output argument vvect is the vector containing the same data as the .pnt file.

varx is a column vector containing the variances of the real part (that is, also of the imaginary part) of the input Fourier coefficients; varx is an array for multiple inputs. vary is the column vector containing the variances of the real part (that is, also of the imaginary part) of the output Fourier coefficients; vary is an array for multiple outputs.

covxy is the column vector of input-output covariances, covxy = E{conj(Nx)*Ny}. For multiple inputs or outputs, covxy contains just the covariances between input(1) and output(1), or all the covariances beside each other, as [ci1o1,ci1o2,...ci2o1...]. covxy may be empty.

filename is the name of the output file. If the name has no extension, expvar extends it by '.vbn'. If the extension is '.vbn', the result will be a binary file, else an ASCII file. If the extension is '.vnt', no text is sent to the ASCII file, but data.

The file will be created in the active subdirectory or folder. If a file is written or read, the most important values will be displayed on the screen, unless a global variable expimpmessages with value 'no' is defined. If filename is empty, no file will be written.

Variance values will be written to ASCII files by expvar in floating-point form, using 4 digits in the mantissas.

comments is a string with eventual comments (optional), fdate is the date (and time) string (also optional). If fdate is missing or empty, an actual date string will be generated.

Ffile is the associated Fourier vector or file (optional, for cross-checking).

impvar reads variances from variance vectors or files.

vdat is a vector, or the name of the file, or an array of size F-by-2 or F-by-3, [varx,vary] or [varx,vary,covxy]; the vector contains the data in the same order as a *.vnt file.

The file may be an ASCII file with comments (usual extension: .var), an ASCII file without comments (.vnt), or a binary file (.vbn). The file has to be somewhere within the path of MATLAB, or the path is to be explicitly given. The default extension is .vbn.

Examples

expvar(ones(10,1),0.1*ones(10,1),zeros(10,1),'data.vbn');
[varx,vary] = impvar('data.vbn');

Diagnostics

If a file already exists with the same name, expvar tries to delete it. This will be unsuccessful if the file is not in the active subdirectory/folder. In this case the error message is:

Cannot delete existing file ...

If Ffile is given, impvar compares the lengths of the frequency vector and the input and output variance vectors. If they are inconsistent, the error message is:

Data incompatible with Fourier file

expvar and impvar also check the variance vectors for negative, complex, infinite elements.