Data Objects

Objects  tiddata  and fiddata  implement the storage of measured or preprocessed data (see help(tiddata) or help(fiddata)). They are the children of the generic object iddat . Their constructors are the function M-files tiddata and fiddata. For the objects both the functions set/get, and the structure-like references work, with the specialty that with get only the nonempty properties are listed, while set lists all properties.

These two objects allow that we can treat all information related to certain data as one single ``variable'', and set the properties in a simple way. A good example is the command plot(obj) which plots the contents of any object in a reasonable form.

fiddata(frdobj)  converts a Frequency Response Data object of the Control System Toolbox to an fiddata object, and frd(fobj) does the conversion in the other direction.

Here are a few examples based on the present implementation.

tdat = tiddata(randn(5,1),2*randn(5,1),100);
get(tdat)
        Version = 1.1
        Date = '20-Aug-1998 19:45:46'
        Input = [5x1 double]
        Output = [5x1 double]
        InputCharacter = 'ZOH'
        OutputCharacter = 'Samples'
        Ts = 100
        ChNumber = 2
        ExpNumber = 1
        SampleNumber = 5
tdat.fs = 150;
fs = tdat.fs
fs =
      150
set(tdat)
        Name:  string
        Version:  version number, set by the system
        Date:  string (date + time)
        Notes:  string
        History:  cell array of strings
        Instrumentation:  structure
        UserData:  user-defined
        Input:  [1x62 char]
        Output:  [1x63 char]
        InputName:  cell array of strings
        OutputName:  cell array of strings
        InputCharacter:  [1x62 char]
        OutputCharacter:  cell array, [ 'Samples' | 'AASamples' ]
        InputUnit:  cell array of strings
        OutputUnit:  cell array of strings
        PeriodLength:  positive scalar, maybe NaN
        Ts:  scalar or cell array
        TStart:  scalar or cell array
        SampleTimes:  vector or cell array

fdat = fiddata(ones(5,1),1./(1+j*2*pi*[1:5]'),[1:5]');
get(fdat)
        Version = 1.1
        Date = '20-Aug-1998 19:55:10'
        Input = [5x1 double]
        Output = [5x1 double]
        InputCharacter = 'AASamples'
        OutputCharacter = 'AASamples'
        InputFreqPoints = [5x1 double]
        OutputFreqPoints = [5x1 double]
        FreqPoints = [5x1 double]
        AllFreqPoints = [5x1 double]
        FreqIndices = [5x1 double]
        ChNumber = 2
        ExpNumber = 1
        FreqNumber = 5
 set(fdat)
        Name:  string
        Version:  version number, set by the system
        Date:  string (date + time)
        Notes:  string
        History:  cell array of strings
        Instrumentation:  structure
        UserData:  user-defined
        Input:  [1x62 char]
        Output:  [1x63 char]
        InputName:  cell array of strings
        OutputName:  cell array of strings
        InputCharacter:  [1x62 char]
        OutputCharacter:  cell array, [ 'Samples' | 'AASamples' ]
        InputUnit:  cell array of strings
        OutputUnit:  cell array of strings
        PeriodLength:  positive scalar, maybe NaN
        InputFrequencies:  vector or cell array
        OutputFrequencies:  vector or cell array
        Frequencies:  vector or cell array
        State:  cell array, [ 'transient' | 'steady-state' ] 
        Synchronization:  string, [ 'on' | 'off' ] 
        InputFreqPoints:  vector or cell array of vectors
        OutputFreqPoints:  vector or cell array of vectors
        FreqPoints:  vector or cell array of vectors
        InputDelay:  array
        OutputDelay:  array
        Fs:  scalar
        InputVariance:  vector (SISO) or cell array (MIMO)
        OutputVariance:  vector (SISO) or cell array (MIMO)
        Covariance:  3-dimensional array, 3rd index: all freq points
        CovVector:  vector (SISO)
        Coherence:  3-dimensional array, 3rd index: all freq points
        CohVector:  vector (SISO)