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jvs:fscan:manual:chapter2:expression:bandpass [2011/09/18 22:26] voyvodic |
jvs:fscan:manual:chapter2:expression:bandpass [2023/02/23 18:43] (current) |
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- | The BANDPASS function will filter out both low and high frequency signals. Usually, frequencies slower than SLOWFREQ and faster than FASTFREQ will be filtered out. | + | The BANDPASS function will filter out both low and high frequency signals |
For convenience, | For convenience, | ||
+ | |||
+ | Note: For temporal filtering, the data set time dimension should have the correct data sampling units (e.g. TR interval) specified; if the time unit is 0 (or negative) a 1s sampling interval is assumed. | ||
SCALEFACT is a scaling factor; FFT output intensity values will be divided by SCALEFACT. Default SCALEFACT is 1000. | SCALEFACT is a scaling factor; FFT output intensity values will be divided by SCALEFACT. Default SCALEFACT is 1000. | ||
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* 1 - frequencies are in Hertz (default: frequencies are seconds) | * 1 - frequencies are in Hertz (default: frequencies are seconds) | ||
* 2 - 2-d spatial filtering [not implemented yet] (default is temporal filtering) | * 2 - 2-d spatial filtering [not implemented yet] (default is temporal filtering) | ||
- | * 4 - make output wordsize same as input (default: output is FLOAT32) | + | * 4 - frequencies are number of cycles across time course (default: seconds or Hertz) |
- | * 8 - filter out 0 frequency (default: 0 freq mean signal is preserved) | + | * 8 - make output wordsize same as input (default: output is FLOAT32) |
+ | * 16 - filter out 0 frequency (default: 0 freq mean signal is preserved) | ||
+ | * 32 - no filtering (test FFT -> reverse FFT) | ||
Example:\\ | Example:\\ | ||
- | --expr bandpass 0 30 3 ; filter out frequencies below 30s (0.033 Hz) and above 3s (0.33 Hz) | + | < |
- | --expr bandpass 1 0.033 0.33 ; same as above | + | -expr bandpass 0 30 3 ; filter out frequencies below 30s (0.033 Hz) and above 3s (0.33 Hz) |
- | | + | |
+ | | ||
+ | -expr bandpass 0 10 40 ; filter out frequencies between 10s (0.1 Hz) and 40s (0.025 Hz) | ||
+ | </ | ||
**See Also:**\\ | **See Also:**\\ |