R: Plot Regression Coefficients of PLSR and PCR models

coefplot {pls} | R Documentation

## Plot Regression Coefficients of PLSR and PCR models

### Description

Function to plot the regression coefficients of an `mvr` object.

### Usage

    coefplot(object, ncomp = object$ncomp, comps, intercept = FALSE,
             separate = FALSE, se.whiskers = FALSE, nCols, nRows, labels,
             type = "l", lty, lwd = NULL, pch, cex = NULL, col, legendpos,
             xlab = "variable", ylab = "regression coefficient", main,
             pretty.xlabels = TRUE, xlim, ylim,
             ask = nRows * nCols < nPlots && dev.interactive(), ...)

### Arguments

`object` | an `mvr` object. The fitted model.
`ncomp, comps` | vector of positive integers. The components to plot. See `coef.mvr` for details.
`separate` | logical. If `TRUE`, coefficients for different model sizes are blotted in separate plots.
`se.whiskers` | logical. If `TRUE`, whiskers at plus/minus 1 estimated standard error are added to the plot. This is only available if the model was cross-validated with `jackknife = TRUE`. Also, in the current implementation, `intercept` must be `FALSE`, and `separate` must be `TRUE` if `length(ncomp) > 1`.
`intercept` | logical. Whether coefficients for the intercept should be plotted. Ignored if `comps` is specified. Defaults to `FALSE`. See `coef.mvr` for details.
`nCols, nRows` | integer. The number of coloumns and rows the plots will be laid out in. If not specified, `coefplot` tries to be intelligent.
`labels` | optional. Alternative x axis labels. See Details.
`type` | character. What type of plot to make. Defaults to `"l"` (lines). Alternative types include `"p"` (points) and `"b"` (both). See `plot` for a complete list of types.
`lty` | vector of line types (recycled as neccessary). Line types can be specified as integers or character strings (see `par` for the details).
`lwd` | vector of positive numbers (recycled as neccessary), giving the width of the lines.
`pch` | plot character. A character string or a vector of single characters or integers (recycled as neccessary). See `points` for all alternatives.
`cex` | numeric vector of character expansion sizes (recycled as neccessary) for the plotted symbols.
`col` | character or integer vector of colors for plotted lines and symbols (recycled as neccessary). See `par` for the details.
`legendpos` | Legend position. Optional. Ignored if `separate` is `TRUE`. If present, a legend is drawn at the given position. The position can be specified symbolically (e.g., `legendpos = "topright"`). This requires R >= 2.1.0. Alternatively, the position can be specified explicitly (`legendpos = t(c(x,y))`) or interactively (`legendpos = locator()`). This only works well for plots of single-response models.
`xlab,ylab` | titles for x and y axes. Typically character strings, but can be expressions (e.g., `expression(R^2)` or lists. See `title` for details.
`main` | optional main title for the plot. See Details.
`pretty.xlabels` | logical. If `TRUE`, `coefplot` tries to plot the x labels more nicely. See Details.
`xlim,ylim` | optional vector of length two, with the x or y limits of the plot.
`ask` | logical. Whether to ask the user before each page of a plot.
`...` | Further arguments sent to the underlying plot functions.

### Details

`coefplot` handles multiple responses by making one plot for each response. If `separate` is `TRUE`, separate plots are made for each combination of model size and response. The plots are laid out in a rectangular fashion.

If `legendpos` is given, a legend is drawn at the given position (unless `separate` is `TRUE`).

The argument `labels` can be a vector of labels or one of `"names"` and `"numbers"`. The labels are used as x axis labels. If `labels` is `"names"` or `"numbers"`, the variable names are used as labels, the difference being that with `"numbers"`, the variable names are converted to numbers, if possible. Variable names of the forms "number" or "number text" (where the space is optional), are handled.

The argument `main` can be used to specify the main title of the plot. It is handled in a non-standard way. If there is only on (sub) plot, `main` will be used as the main title of the plot. If there is more than one (sub) plot, however, the presence of `main` will produce a corresponding ‘global’ title on the page. Any graphical parametres, e.g., `cex.main`, supplied to `coefplot` will only affect the ‘ordinary’ plot titles, not the ‘global’ one. Its appearance can be changed by setting the parameters with `par`, which will affect both titles. (To have different settings for the two titles, one can override the `par` settings with arguments to `coefplot`.)

The argument `pretty.xlabels` is only used when `labels` is specified. If `TRUE` (default), the code tries to use a ‘pretty’ selection of labels. If `labels` is `"numbers"`, it also uses the numerical values of the labels for horisontal spacing. If one has excluded parts of the spectral region, one might therefore want to use `pretty.xlabels = FALSE`.

When `separate` is `TRUE`, the arguments `lty`, `col`, and `pch` default to their `par()` setting. Otherwise, the default for all of them is `1:nLines`, where `nLines` is the number of model sizes specified, i.e., the length of `ncomp` or `comps`.

The function can also be called through the `mvr` plot method by specifying `plottype = "coefficients"`.

### Note

`legend` has many options. If you want greater control over the appearance of the legend, omit the `legendpos` argument and call `legend` manually.

The handling of `labels` and `pretty.xlabels` is experimental.

### Author(s)

Ron Wehrens and Bjørn-Helge Mevik

### See Also

`mvr`, `plot.mvr`, `coef.mvr`, `plot`, `legend`

### Examples

    data(yarn)
    mod.nir <- plsr(density ~ NIR, ncomp = 8, data = yarn)
    ## Not run:
    coefplot(mod.nir, ncomp = 1:6)
    plot(mod.nir, plottype = "coefficients", ncomp = 1:6) # Equivalent to the previous
    ## Plot with legend:
    coefplot(mod.nir, ncom = 1:6, legendpos = "bottomright")

    ## End(Not run)

    data(oliveoil)
    mod.sens <- plsr(sensory ~ chemical, ncomp = 4, data = oliveoil)
    ## Not run: coefplot(mod.sens, ncomp = 2:4, separate = TRUE)

[Package pls version 2.6-0 Index]