RSEIS (version 4.2-4)

DECIMATE.SEISN: 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 )

Value

an RSEIS list.

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

Author

Jonathan M. Lees<[e-mail]>

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.

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 )