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reference:ft_freqsimulation [2018/08/23 14:43] (current)
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 +=====  FT_FREQSIMULATION =====
 +
 +Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_freqsimulation"​.
 +
 +<​html><​pre>​
 +  <a href=/​reference/​ft_freqsimulation><​font color=green>​FT_FREQSIMULATION</​font></​a>​ makes simulated data in FieldTrip format. The data is
 +  built up from fifferent frequencies and can contain a signal in which the
 +  different frequencies interact (i.e. cross-frequency coherent). Different
 +  methods are possible to make data with special properties.
 + 
 +  Use as
 +    [data] = ft_freqsimulation(cfg)
 + 
 +  The configuration options can include
 +    cfg.method ​    = The methods are explained in more detail below, but they can be
 +                      '​superimposed' ​   simply add the contribution of the different frequencies
 +                      '​broadband' ​      ​create a single broadband signal component
 +                      '​phalow_amphigh' ​ phase of low freq correlated with amplitude of high freq
 +                      '​amplow_amphigh' ​ amplitude of low freq correlated with amplithude of high freq
 +                      '​phalow_freqhigh'​ phase of low freq correlated with frequency of high signal
 +                      '​asymmetric' ​     single signal component with asymmetric positive/​negative deflections
 +    cfg.output ​    = which channels should be in the output data, can be '​mixed'​ or '​all'​ (default = '​all'​)
 +    cfg.randomseed = '​yes'​ or a number or vector with the seed value (default = '​yes'​)
 + 
 +  The number of trials and the time axes of the trials can be specified by
 +    cfg.fsample ​   = simulated sample frequency
 +    cfg.trllen ​    = length of simulated trials in seconds
 +    cfg.numtrl ​    = number of simulated trials
 +  or by
 +    cfg.time ​      = cell-array with one time axis per trial, which are for example obtained from an existing dataset
 + 
 +  For each of the methods default parameters are configured to generate
 +  example data, including noise. To get full control over the generated
 +  data you should explicitely set all parameters involved in the method
 +  of your choise. The interpretation of the following signal components
 +  depends on the specified method:
 + 
 +  cfg.s1.freq ​    = frequency of signal 1
 +  cfg.s1.phase ​   = phase (in rad) relative to cosine of signal 1  (default depends on method)
 +                  = number or '​random'​
 +  cfg.s1.ampl ​    = amplitude of signal 1
 +  cfg.s2.freq ​    = frequency of signal 2
 +  cfg.s2.phase ​   = phase (in rad) relative to cosine of signal 1  (default depends on method)
 +                  = number or '​random'​
 +  cfg.s2.ampl ​    = amplitude of signal 2
 +  cfg.s3.freq ​    = frequency of signal 3
 +  cfg.s3.phase ​   = phase (in rad) relative to cosine of signal 1  (default depends on method)
 +                  = number or '​random'​
 +  cfg.s3.ampl ​    = amplitude of signal 3
 +  cfg.s4.freq ​    = frequency of signal 4
 +  cfg.s4.phase ​   = phase (in rad) relative to cosine of signal 1  (default depends on method)
 +                  = number or '​random'​
 +  cfg.s4.ampl ​    = amplitude of signal 4
 + 
 +  cfg.n1.ampl ​    = root-mean-square amplitude of wide-band signal prior to filtering
 +  cfg.n1.bpfreq ​  = [Flow Fhigh]
 +  cfg.n2.ampl ​    = root-mean-square amplitude of wide-band signal prior to filtering
 +  cfg.n2.bpfreq ​  = [Flow Fhigh]
 + 
 +  cfg.asymmetry ​  = amount of asymmetry (default = 0, which is none)
 +  cfg.noise.ampl ​ = amplitude of noise
 + 
 + 
 +  In the method '​superimposed'​ the signal contains just the sum of the different frequency contributions:​
 +      s1: first frequency
 +      s2: second frequency
 +      s3: third frequency
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = s1 + s2 + s3 + noise
 +      2nd channel: s1
 +      3rd channel: s2
 +      4th channel: s3
 +      5th channel: noise
 + 
 +  In the method '​broadband'​ the signal contains a the superposition of two
 +  broadband signal components, which are created by bandpass filtering a
 +  Gaussian noise signal:
 +      n1: first broadband signal
 +      n2: second broadband signal
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = n1 + n2 + noise
 +      2nd channel: n1
 +      3rd channel: n2
 +      4th channel: noise
 + 
 +  In the method '​phalow_amphigh'​ the signal is build up of 4 components; s1, s2, s3 and noise:
 +      s1: amplitude modulation (AM), frequency of this signal should be lower than s2
 +      s2: second frequency, frequncy that becomes amplitude modulated
 +      s3: DC shift of s1, should have frequency of 0
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = (s1 + s3)*s2 + noise,
 +      2nd channel: s1
 +      3rd channel: s2
 +      4th channel: s3
 +      5th channel: noise
 + 
 +  In the method '​amplow_amphigh'​ the signal is build up of 5 components; s1, s2, s3, s4 and noise.
 +      s1: first frequency
 +      s2: second frequency
 +      s3: DC shift of s1 and s2, should have frequency of 0
 +      s4: amplitude modulation (AM), frequency of this signal should be lower than s1 and s2
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = (s4 + s3)*s1 + (s4 + s3)*s2 + noise,
 +      2nd channel: s1
 +      3rd channel: s2
 +      4th channel: s3
 +      5th channel: noise
 +      6th channel: s4
 +      7th channel: mixed part 1: (s4 + s3)*s1
 +      8th channel: mixed part 2: (s4 + s3)*s2
 + 
 +  In the method '​phalow_freqhigh'​ a frequency modulated signal is created.
 +    signal is build up of 3 components; s1, s2 and noise.
 +      s1: represents the base signal that will be modulated
 +      s2: signal that will be used for the frequency modulation
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = s1.ampl * cos(ins_pha) + noise
 +      2nd channel: s1
 +      3rd channel: s2
 +      4th channel: noise
 +      5th channel: inst_pha_base ​  ​instantaneous phase of the high (=base) frequency signal s1
 +      6th channel: inst_pha_mod ​   low frequency phase modulation, this is equal to s2
 +      7th channel: inst_pha ​       instantaneous phase, i.e. inst_pha_base + inst_pha_mod
 + 
 +  In the method '​asymmetric'​ there is only one periodic signal, but that
 +  signal is more peaked for the positive than for the negative deflections.
 +  The average of the signal over time is zero.
 +      s1: represents the frequency of the base signal
 +  and the output consists of the following channels:
 +      1st channel: mixed signal = asymmetric signal + noise
 +      2nd channel: sine wave with base frequency and phase, i.e. s1
 +      3rd channel: asymmetric signal
 +      4th channel: noise
 + 
 +  See also <a href=/​reference/​ft_freqanalysis><​font color=green>​FT_FREQANALYSIS</​font></​a>,​ <a href=/​reference/​ft_timelocksimulation><​font color=green>​FT_TIMELOCKSIMULATION</​font></​a>,​ <a href=/​reference/​ft_dipolesimulation><​font color=green>​FT_DIPOLESIMULATION</​font></​a>,​
 +  <a href=/​reference/​ft_connectivitysimulation><​font color=green>​FT_CONNECTIVITYSIMULATION</​font></​a>​
 +</​pre></​html>​