DECIMATE.SEISN: Decimate a set of traces

In RSEIS: Seismic Time Series Analysis Tools

Decimate a set of traces

Description

Decimate, or reduce the sample rate of a set of traces stored in event RSEIS format

Usage

DECIMATE.SEISN(TH, sel=1:length(TH$JSTR), dec=5 ,
 type="LP", proto="BU" , fl=2,  fh=10, RM=FALSE, zp=TRUE )

Arguments

TH	RSEIS list
sel	numeric, which traces to select
dec	numeric, number of samples to skip
type	type of filter (see butfilt), or FALSE for no filter
proto	filter proto type
fl	low pass frequency cut off
fh	high pass frequency cut off
RM	Remove mean value from trace, default=FALSE
zp	zero phase filter, default=TRUE

Details

Reduces the number of samples by skipping every "dec" sample.

To achieve smoothing prior to sampling, low pass filter may be applied to avoid spikes or other sampling issues.

If type is FALSE, no filter is applied and samples are taken from the input.

Value

an RSEIS list.

Note

The dt, n and t2 are modified in info.

Author(s)

Jonathan M. Lees<[e-mail]>

See Also

butfilt, downsample

Examples

data(GH)

dec = 250/50

#####  resample all traces by reducing from 250 to 50 samples/s
DH = DECIMATE.SEISN(GH, sel=1:length(GH$JSTR), dec=dec ,
 type="LP", proto="BU" , fl=2,  fh=50, RM=FALSE, zp=TRUE )

#####  compare

#####   times in
### starting second should be the same
GH$info$sec[1:5]  - DH$info$sec[1:5] 
####  number of samples should be reduced
cbind(GH$info$n[1:5] , DH$info$n[1:5]  )
### ending seconds should be close but not identical
cbind(GH$info$t2[1:5] , DH$info$t2[1:5]  )

cbind(GH$info$dt[1:5] , DH$info$dt[1:5]  )

cbind( sapply(GH$JSTR, 'length'), sapply(DH$JSTR, 'length') )



####  for visual comparison:
### par(mfrow=c(2,1) )
## g =  swig(GH, sel=which(GH$COMPS=="V" ), SHOWONLY=0 )
## d =  swig(DH, sel=which(DH$COMPS=="V" ), SHOWONLY=0 )

  

RSEIS documentation built on Sept. 13, 2024, 1:09 a.m.