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function sys = dataSlice(data,Start,End,Freq)
// Select sample data from iddata
//
// Calling Sequence
// h = dataSlice(plantData,Start,End,Ts)
// Parameters
// data : iddata type
// Start : non-negative integer index
// End : non-negative integer index, always greater than Start index
// Ts : sampling frequency, default value is 1
// Description
// Extracts the samples in between Start and End index of the plant time series data,iddata type. For specified sampling frequency, it resamples the extracted data.
//
// Examples
// a = [1 0.5];b = [0 0.2 0.3];
// sys = idpoly(a,b,'Ts',0.1)
// u = idinput(1024,'PRBS',[0 1/20],[-1 1])
// y = sim(u,sys)+rand(1024,1)
// plantData = iddata(y,u,0.1)
// h = dataSlice(plantData,1,20,0.1)
// Authors
// Ashutosh Kumar Bhargava,Bhushan Manjarekar
[lhs,rhs] = argn()
// storing the model data
modelData = data
// storing the statrting point
try
startData = Start
catch
startData = 1
end
// storing the end point
try
endData = End
catch
endData = LastIndex(data)
end
// Storing the frequency
try
freqData = Freq
catch
freqData = 1
end
// error message generate
if startData > endData then
error(msprintf(gettext("%s:Start index can not greater than End index.\n"),"dataSlice"))
end
if size(startData,'*') ~= 1 then
error(msprintf(gettext("%s:Start index must be non negative scalar integer number.\n"),"dataSlice"))
end
if size(endData,'*') ~= 1 then
error(msprintf(gettext("%s:End index must be non negative scalar integer number.\n"),"dataSlice"))
end
if ~freqData || size(freqData,'*') ~= 1 then
error(msprintf(gettext("%s:Frequency must be non negative scalar number.\n"),"dataSlice"))
end
// --------------------------------------------------------------------------
if typeof(modelData) == 'constant' then
Ts = 1
elseif typeof(modelData) == 'iddata' then
Ts = modelData.Ts
end
// --------------------------------------------------------------------------
if freqData> Ts || modulo(Ts,freqData) then
warning(msprintf(gettext("%s:inconsistent frequency.\n"),"dataSlice"))
freqData = Ts
end
if typeof(modelData) == 'constant' then
temp = modelData(startData:Ts/freqData:endData,:)
elseif typeof(modelData) == 'iddata' then
tempY = modelData.OutputData;tempU = modelData.InputData
if ~size(tempY,'r') then
tempY = []
else
tempY = tempY(startData:Ts/freqData:endData,:);
end
if ~size(tempU,'r') then
tempU = []
else
tempU = tempU(startData:Ts/freqData:endData,:)
end
temp = iddata(tempY,tempU,Ts/freqData)
temp.TimeUnit = modelData.TimeUnit
end
sys = temp
endfunction
function varargout = LastIndex(modelData)
// finding the sample size
if typeof(modelData) == "constant" then
varargout(1) = length(modelData(:,1))
elseif typeof(modelData) == "iddata" then
temp = max(size(modelData.OutputData,'r'),size(modelData.InputData,'r'))
varargout(1) = temp
end
endfunction
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