lowpass {astrochron} | R Documentation |

## Lowpass filter stratigraphic series

### Description

Lowpass filter stratigraphic series using rectangular, Gaussian or tapered cosine window. This function can also be used to highpass filter a record (see examples).

### Usage

```
lowpass(dat,padfac=2,fcut=NULL,win=0,demean=T,detrend=F,addmean=T,alpha=3,p=0.25,
xmin=0,xmax=Nyq,genplot=T,verbose=T)
```

### Arguments

`dat` |
Stratigraphic series for lowpass filtering. First column should be location (e.g., depth), second column should be data value. |

`padfac` |
Pad with zeros to (padfac*npts) points, where npts is the original number of data points. |

`fcut` |
Cutoff frequency for lowpass filtering. |

`win` |
Window type for bandpass filter: 0 = rectangular , 1= Gaussian, 2= Cosine-tapered window. |

`demean` |
Remove mean from data series? (T or F) |

`detrend` |
Remove linear trend from data series? (T or F) |

`addmean` |
Add mean value to bandpass result? (T or F) |

`alpha` |
Gaussian window parameter: alpha is 1/stdev, a measure of the width of the Dirichlet kernal. Larger values decrease the width of data window, reduce discontinuities, and increase width of the transform. Choose alpha >= 2.5. |

`p` |
Cosine-tapered window parameter: p is the percent of the data series tapered (choose 0-1). |

`xmin` |
Smallest frequency for plotting. |

`xmax` |
Largest frequency for plotting. |

`genplot` |
Generate summary plots? (T or F) |

`verbose` |
Verbose output? (T or F) |

### See Also

`bandpass`

, `noKernel`

, `noLow`

, `prewhiteAR`

, `prewhiteAR1`

, and `taner`

### Examples

```
# generate example series with periods of 405 ka, 100 ka, 40ka, and 20 ka, plus noise
ex=cycles(freqs=c(1/405,1/100,1/40,1/20),end=1000,dt=5,noisevar=.1)
# lowpass filter eccentricity terms using cosine-tapered window
lowpass_ex=lowpass(ex,fcut=.02,win=2,p=.4)
# highpass filter obliquity and precession terms using cosine-tapered window
# if you'd like the final notch filtered record to be centered on the mean proxy
# value, set addmean=FALSE
highpass_ex=lowpass(ex,fcut=.02,win=2,p=.4,addmean=FALSE)
highpass_ex[2] <- ex[2]-highpass_ex[2]
pl(2)
plot(ex,type="l",main="Eccentricity+Obliquity+Precession")
plot(highpass_ex,type="l",main="Obliquity+Precession highpassed signal")
```

*astrochron*version 1.3 Index]