2.11.1.1 fft1

1 Menu Information
2 Brief Information
3 Additional Information
4 Command Line Usage
5 X-Function Execution Options
6 Variables
7 Examples
8 More Information
9 Related X-Functions

Menu Information

Analysis: Signal Processing: FFT: FFT

Brief Information

Compute fourier transform

Additional Information

This feature is updated in 8.0 SR5.

Command Line Usage

1. fft1 ix:=Col(1); 
2. fft1 ix:=(col(2),col(3)); 
3. fft1 ix:=Col(1) interval:=2; 
4. fft1 ix:=Col(1) win:=hanning correct:=power; 
5. fft1 ix:=Col(1) shift:=1; 
6. fft1 ix:=Col(1) psd:=1 norm:=ssa st:=oneside;

X-Function Execution Options

Please refer to the page for additional option switches when accessing the x-function from script

Variables

Display Name	Variable Name	I/O and Type	Default Value	Description
Input	ix	Input vector<complex>	<active>	Specifies the input signal, which could be complex. The real and imaginary parts of the signal can be saved in different columns or in the same column. The default is <Active>, which corresponds to the active dataset.
Sampling Interval	interval	Input double	1	Specifies the sampling interval. The default is <Auto>, which corresponds to an automatically-computed interval. Please see the algorithm part for details.
Window	win	Input int	rect	Specifies the type of window to be used for suppressing the leakage. Please see the algorithm part for details. Option list 0=rect:Rectangle Rectangular window 1=welch:Welch Welch window 2=tri:Triangular Triangular window 3=bartlett:Bartlett Bartlett window 4=hanning:Hanning Hanning window 5=hamming:Hamming Hamming window 6=blackman:Blackman Blackman window 7=gauss:Gaussian Gaussian window 8=kaiser:Kaiser Kaiser window
Alpha	alpha	Input double	0	This variable is only available when window type is Gaussian. It specifies the Alpha parameter (the reciprocal of the standard deviation) for Gaussian window.
Beta	beta	Input double	0	This variable is only available when window type is Kaiser. It specifies the Beta parameter for Kaiser window.
Window Correction	correct	Input int	amplitude	Specifies the Window Correction Factor used to correct the alteration made by applying a window to the input data. Option list none:None No correction is applied. amp:Amplitude Amplitude Correction is applied. power:Power Energy Correction is applied.
Reserved	Reserved	Input int	0	This is a reserved variable. It has no effect on the computation.
Normalize Re, Im and Mag	norma	Input int	0	Specifies whether to normalize the complex, real, imaginary, magnitude and sqaure magnitude output. The default is false. Note that other outputs such as amplitude are not affected by this variable. Please see the algorithm section for details.
Shift	shift	Input int	1	Specifies whether the result should be rearranged so that the lower frequency components are in the center.
Unwrap phase	unwrap	Input int	1	Specifies whether the phase should be unwrapped. If wrapped, Phase angle is modulo reduced to be between + and - 180 degrees.
Factor	factor	Input int	ee	Specifies whether the Electrical Engineering or Science convention is used to set the sign of the Exponential Phase factor. Option list ee:-1 (Electrical Engineering) The phase factor sign will be opposite to that of the Science option. science:+1 (Science) The phase factor will be set according to the formulae listed in page 503 of Numerical Recipes in C, 2nd edition
Spectrum Type	st	Input int	auto	Specifies the Nyquist interval over which power is calculated. Note that this will also affect the computation of other results. Option list auto:<auto> If the input signal is real, one-sided power will be chosen; otherwise, two-sided power will be selected. When this option is selected, Origin will look at the input data to determine whether it is complex or not. If the input data is stored in a column of the Complex data type, but the data contains only a real part, Origin will regard it as real, and not as complex, resulting in a one-sided spectrum. Alternately, if the input data has an all-zero column as the imaginary part, Origin will also regard the input as real, and produce a one-sided spectrum. oneside:One -sided One-sided power will be computed. twoside:Two -sided Two-sided power will be computed.
Normalize power to	norm	Input int	msa	Specifies the power density normalization method. Please see the algorithm part for detail. Option list msa:MSA-Mean Square Amplitude Mean square amplitude method ssa:SSA-Sum Square Amplitude Sum square amplitude method tisa:TISA-Time Interval Square Amplitude Time Integral square amplitude method
Preview	pre	Input int	ap	Specifies the preview content in the dialog. Option list none:None NONE ap:Amplitude /Phase Both the amplitude and the phase. pp:Power /Phase Both the power and the phase. amp:Amplitude The amplitude img:Imaginary The imaginary parts of the transformed data mag:Magnitude The magnitude phase:Phase The phase power:Power The power spectrum or power density real:Real The real parts of the transformed data ri:Real /Imaginary Both the real parts and imaginary parts of the transformed data db:dB The amplitude in dB. ndb:Normalized dB The normalized amplitude in dB. rms:RMS Amplitude The RMS amplitude. sqamp:Square Amplitude The square amplitude. sqmag:Square Magnitude The square magnitude.
Real	re	Input int	1	Specifies whether or not to output a graph of the real parts of the FFT result.
Imag	im	Input int	1	Specifies whether or not to output a graph of the imaginary parts of the FFT result.
Amplitude/Phase	ap	Input int	1	Specifies whether or not to output a combined graph of amplitude and phase.
Phase	phase	Input int	0	Specifies whether or not a graph of the phase will be outputted.
Power/Phase	pp	Input int	0	Specifies whether or not to output a graph of the phase.
Real/Imag	ri	Input int	1	Specifies whether or not to output a combined graph of power and phase.
Magnitude	mag	Input int	1	Specifies whether or not to output a graph of the magnitude.
Amplitude	amp	Input int	0	Specifies whether or not to output a graph of the amplitude.
Power	psd	Input int	1	Specifies whether or not to output a graph of the power.
dB	db	Input int	1	Specifies whether or not to output a graph of the result of dB.
Normalized dB	ndb	Input int	0	Specifies whether or not to output a graph of the result of normalized dB.
RMS Amplitude	rms	Input int	0	Specifies whether or not to output a graph of the RMS amplitude.
Square Amplitude	sqr_amp	Input int	0	Specifies whether or not to output a graph of the squared amplitude.
Square Magnitude	sqr_mag	Input int	0	Specifies whether or not to output a graph of the squared magnitude.
Result Data Sheet	rd	Output ReportData	[<input>]<new>	Specifies the output data sheet.
Result Graph Sheet	rt	Output ReportTree	[<input>]<new template:=graph>	Specifies the output graph sheet.

Examples

To perform 1D FFT using default settings on data in columns 2 of the active worksheet, use the script command:

fft1 col(2)

Code Sample

// This example plots two different FFT Amplitudes from two date ranges of sunspot data to illustrate the ~11 year sunspot cycle
// Import the data
string fname$ = system.path.program$ + "Samples\Signal Processing\dayssn.dat";
//col(1) = year, col(2)=month, col(3)=day, 
//col(4) = date values in contiguous year with fractions
//col(5) = observation
//so we should have a sheet with 5 col and col(4)=X col(5)=Y
newbook s:=0;newsheet cols:=5 xy:="NNNXY"; 
impasc;
// Interpolate to replace missing values and put result to col(6)
interp1q 4 (4,5) 6;
// this is our data
range rData1 = 6[1:14609];// row range for years 1818 to 1858
range rData2 = 6[54057:end];// row range for years 1966 - 2006

// now start the FFT with the fft1 X-Function which will create a ReportData sheet and a ReportTable sheet
fft1 rData1;
//after running an XF, a tree with same name is created, here we will make use of fft1.rd the ReportData node
range rReportData1=fft1.rd$;//range to hold the Report Data from the FFT result
range rAmp1=%(rReportData1.getlayer()$)col(Amplitude);
rAmp1[C]$="1818 - 1858"; // change the Comment to make better legend for the graph
fft1 rData2;
range rReportData2=fft1.rd$;
range rAmp2=%(rReportData2.getlayer()$)col(Amplitude);
rAmp2[C]$="1966 - 2006";
 
// Open a new empty graph. Use your own template if needed.
win -t plot;
// Plot output to active graph layer
plotxy rAmp1 plot:=200 color:=color(red) o:=<active>;
plotxy rAmp2 plot:=200 color:=color(blue) o:=<active>;
// Zoom in to show the peak
x1=0;x2=0.5;y1=0;y2=100;
// Mark 11 years with a vertical line 
draw -n peakval -l -v 1/11; 
peakval.linewidth = 3;
peakval.color = color(orange);
// and add a text label
label -n peaklabel \b(11 Year Cycle of Sunspots);
peaklabel.x = peakval.x + 1.1 * peaklabel.dx / 2;
peaklabel.y = (y1 + y2) / 2;
peaklabel.fsize = 30;