expfou, impfou (Frequency Domain Identification Toolbox)

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

Fvect = expfou(freqvect,x,y)
Fvect = expfou(freqvect,x,y,i,expno,... filename,comments,fdate,digitnum)
[freqvect,x,y] = impfou(Fdat)
[freqvect,x,y,expno,comments,fdate] = impfou(Fdat,expi)

Description

expfou exports data of one experiment (or several experiments) to a vector in the workspace, and/or to a (perhaps already existing) Fourier file.

The output argument Fvect is the vector containing the same data as would be sent to a *.fnt file.

freqvect is the vector of frequency points, x is the complex input amplitude vector (or array for multiple inputs), and y is the complex output amplitude vector (or array for multiple outputs). Each amplitude vector must be a column vector. The amplitudes belonging to different experiments have to be put under each other. x or y may be empty, but both of them have to be given.

expno is the total number of experiments. i contains the number(s) of the actual experiment(s). If several experiments are given, they must be denoted by successive numbers. If i is empty, the default is i = [1:length(x(:,1))/length(freqvect)].

The string filename contains the name of the output file. If this name has no extension, expfou extends it by '.fbn'. If the extension is .fbn, the result will be a binary file, else an ASCII file. If the extension is .fnt, no text is sent to the ASCII file, only data.

The file will be created in the active subdirectory or folder. If filename is empty, no file will be generated.

If a file is read or written, the most important values will be displayed on the screen, unless a global variable expimpmessages with value 'no' is defined.

When exporting the data of the first experiment, any file with the same name will be deleted.

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

Amplitude values will be written to ASCII files by expfou in floating-point form. digitnum is the number of digits of mantissas, sent to ASCII files, with the limits 1 digitnum 16, and default value 7.

impfou reads complex amplitudes from Fourier vectors or files. The file may be an ASCII file with comments (usual extension: .fou), a so-called flat ASCII file without comments (.fnt), or a binary file (.fbn). The file has to be somewhere within the path of MATLAB, or the path is to be explicitly given. The default extension is .fbn.

The input argument Fdat of impfou is the data vector, or the name of a file, or may be an array of size F-by-3 in order to be able to process directly any output format of other M-files. The data vector contains the data in the same order as a *.fnt file, and the array is [freqv,x,y].

expi contains the number(s) of the experiment(s) to be read (integer vector). expi is optional; if it is omitted or empty, all the experiments will be read.

Default Argument Values

digitnum = 7,  i = [1:length(x(:,1))/length(freqvect)],
expno = max(i)

Examples

expfou([1:20],ones(100,1),0.1*ones(100,1),...
          [1:5],5,'data.fbn');
[freqvect,x,y,expno] = impfou('data.fbn');

Send results of experiments in two steps:

Fvect = expfou([1:20],ones(60,1),0.1*ones(60,1),[1:3],5);
Fvect = [Fvect;expfou([1:20],...
     ones(40,1),0.1*ones(40,1),[4,5],5)];
[freqvect,x,y,expno] = impfou(Fvect);

Diagnostics

If not experiment No. 1 is being exported to a file, expfou looks for an already existing file. If this is not found, the error message is

File has to exist already when exporting ... experiment

If a file already exists with the same name, and the first experiment is being exported, expfou 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 ...

impfou checks the validity of the contents of the vector (file). If it is not consistent, an error message is sent:

Not enough data in file ...

or if the vector is too long, a warning message is displayed:

Number of data is incorrect in file ...