Working with TRIM command files and TRIM data files

TRIM Command Files

The original TRIM software can be controlled with text files containing a series of commands that specify both the location and format of the data, an the model (or models) to compute. Such TRIM command files (usually stored with the extension .tcf) should be considered legacy but for backwards compatability they can be used from R.

To try this, execute the code below to create a tcf file and a TRIM data file in the current working directory of R.

library(rtrim)
tmp <- "FILE skylark.dat
TITLE  skylark-1d
NTIMES 8
NCOVARS 2
LABELS
Habitat
Cov2
END
MISSING 999
WEIGHT Absent
COMMENT Example 1; using linear trend model
WEIGHTING off
OVERDISP on
SERIALCOR on
MODEL 2
"
write(tmp,file="skylark.tcf")
data(skylark)
skylark[is.na(skylark)] <- 999
write.table(skylark,file="skylark.dat",col.names=FALSE,row.names=FALSE)

Executing a TRIM command file is as easy as reading the file using read_tcf and passing the result to trim.

tc <- read_tcf("skylark.tcf")
m <- trim(tc)

The resulting trim object can be evaluated as described in the getting started vignette. For example

wald(m)

## Wald test for significance of slope parameter
##   Wald = 11.69, df=1, p=0.000630

The object tc, resulting from read_tcf is an object of class trimcommand. It stores all commands defined in the TRIM command file. Note that logical parameters such as WEIGHT are transformed to logical in R.

tc

## Object of class trimcommand:
##         file: skylark.dat
##        title: skylark-1d
##       ntimes: 8
##      ncovars: 2
##       labels: Habitat, Cov2
##      missing: 999
##       weight: FALSE
##      comment: Example 1; using linear trend model
##    weighting: FALSE
##    serialcor: TRUE
##     overdisp: TRUE
##     basetime: 
##        model: 2
##   covariates: 
## changepoints: 
##     stepwise: 
##   autodelete: 
##  outputfiles: 
## overallchangepoints: 
##    impcovout: FALSE
##        covin: FALSE

NOTE. Be aware that R has its own present working directory. If relative paths (that is, file names not starting with the full path to their location) are used in the TRIM command file, R wil interpret them as relative to the current working directory.

TRIM data files

TRIM data files are basically space-separated, tabular tekstfiles where the order and type of columns is fixed by a few parameters. Given such a specification, a file can be read with read_tdf.