interp {biogas} | R Documentation |

## Interpolate Biogas Composition or Cumulative Production

### Description

`interp`

interpolates (or extrapolates) biogas composition (methane concentration) or cumulative production data to a wanted time using one of several possible methods.

### Usage

```
interp(times, y, time.out, method = "linear", extrap = FALSE)
```

### Arguments

`times` |
measurement times.
Numeric vector or |

`y` |
response variable at |

`time.out` |
time or times at which interpolated values are needed.
Numeric vector or |

`method` |
method used for interpolation.
Default is |

`extrap` |
should |

### Details

`interp`

is really a wrapper for the interpolation functions `approx`

and `spline`

.
For cumulative production, which (usually) must monotonically increase, `method = "hyman"`

is the best choice.
Extrapolation behavior depends on `method`

.
For `method = "linear"`

, `extrap = TRUE`

simply returns the value of the closest `y`

.
For manometric measurement with mix of venting/no venting with composition measurements only when venting use `method = "f1"`

.
See `approx`

and `spline`

for more information.

### Value

Interpolated estimates of `y`

at given `times`

.

### Author(s)

Sasha D. Hafner and Charlotte Rennuit

### See Also

### Examples

```
# Fake composition data
dat <- data.frame(time = c(1, 7, 14, 28),
xCH4 = c(0.3, 0.5, 0.61, 0.65))
interp(dat$time, dat$xCH4, time.out = 10)
interp(dat$time, dat$xCH4, time.out = 10, method = "natural")
interp(dat$time, dat$xCH4, time.out = c(10, 30))
interp(dat$time, dat$xCH4, time.out = c(10, 30), method = "natural")
interp(dat$time, dat$xCH4, time.out = c(10, 30), extrap = TRUE)
# Actual data
data(comp)
# Work with one reactor
bgc <- subset(comp, id=="2_1")
# With numeric time, interpolate to 1, 7, and 30 days
interp(bgc$days, bgc$xCH4, time.out = c(1, 7, 30))
# If extrapolation is OK
interp(bgc$days, bgc$xCH4, time.out = c(1, 7, 30), extrap = TRUE)
# Or POSIXct
interp(bgc$date.time, bgc$xCH4,
time.out = as.POSIXct("2014-07-12 13:00:00"))
# For cumulative gas production
data(vol)
# Work with one reactor
bgv <- subset(vol, id=="2_1")
# Calculate cumulative volume
bgv <- cumBg(bgv, time.name = "days")
# The interpolate of cumulative production to 1, 7, and 30 days
interp(bgv$days, bgv$cvBg, time.out = c(1, 7, 30), method = "hyman")
```

*biogas*version 1.23.2 Index]