ModelMap (version 2.3.4)

model.interaction.plot: plot of two-way model interactions

Description

Image or Perspective plot of two-way model interactions. Ranges of two specified predictor variables are plotted on X and Y axis, and fitted model values are plotted on the Z axis. The remaining predictor variables are fixed at their mean (for continuous predictors) or their most common value (for categorical predictors).

Usage

model.interaction.plot(model.obj = NULL, x = NULL, y = NULL, 
response.category=NULL, qdata.trainfn = NULL, folder = NULL, 
MODELfn = NULL,  PLOTfn = NULL, pred.means = NULL, xlab = NULL, 
ylab = NULL, x.range = NULL, y.range = NULL, z.range = NULL, 
ticktype = "detailed", theta = 55, phi = 40, smooth = "none", 
plot.type = NULL, device.type = NULL, jpeg.res = 72, 
device.width = 7,  device.height = 7, cex=par()$cex, col = NULL, ...)

Arguments

model.obj

R model object. A RF or SGB model object produced by model.build.

x

String or Integer. Name of predictor variable to be plotted on the x axis. Alternativly, can be a number indicating a variable name from predList.

y

String or Integer. Name of predictor variable to be plotted on the y axis. Alternatively, can be a number indicating a variable name from predList.

response.category

String. Used for categorical response RF models. Specify which category of response variable to use. This category's probabilities will be plotted on the z axis.

qdata.trainfn

String. The name (full path or base name with path specified by folder) of the training data file used for building the model (file should include columns for both response and predictor variables). The file must be a comma-delimited file <

folder

String. The folder used for all output. Do not add ending slash to path string. If folder = NULL (default), a GUI interface prompts user to browse to a folder. To use the working directory, specify folder = getwd().

MODELfn

String. The file name used to save the generated model object, only used if PLOTfn = NULL. If MODELfn is supplied and If PLOTfn = NULL, a graphical file name is generated by pasting MODELfn_plot.type_x.name_y

PLOTfn

String. The file name to use to save the generated graphical plots. The filename can be the full path, or it can be the simple basename, in which case the output will be to the folder specified by folder.

pred.means

Vector. Allows specification of values for other predictor variables. If Null, other predictors are set to their mean value (for continuous predictors) or their most common value (for factored predictors).

xlab

String. Allows manual specification of the x label.

ylab

String. Allows manual specification of the y label.

x.range

Vector. Manual range specification for the x axis.

y.range

Vector. Manual range specification for the y axis.

z.range

Vector. Manual range specification for the z axis.

ticktype

Character: "simple" draws just an arrow parallel to the axis to indicate direction of increase; "detailed" (default) draws normal ticks as per 2D plots. If X or y is factored, ticks will be drawn on both axes.

theta

Numeric. Angles defining the viewing direction. theta gives the azimuthal direction.

phi

Numeric. Angles defining the viewing direction. phi gives the colatitude.

smooth

String. controls smoothing of the predicted surface. Options are "none" (default), "model" which uses a glm model to smooth the surface, and "average" which applies a 3x3 smoothing average. Note: smoothing is not app

plot.type

Character. "persp" gives a 3-D perspective plot. "image" gives an image plot.

device.type

String or vector of strings. Model validation. One or more device types for graphical output from model validation diagnostics. Current choices: lllll{ "default" default graphics device "jpeg"

jpeg.res

Integer. Pixels per inch for jpeg plots. The default is 72dpi, good for on screen viewing. For printing, suggested setting is 300dpi.

device.width

Integer. The device width for diagnostic plots in inches.

device.height

Integer. The device height for diagnostic plots in inches.

cex

Integer. The cex for diagnostic plots.

col

Vector. Color table to use for image plots ( see help file on image for details).

...

additional graphical parameters (see par).

Details

This function provides a diagnostic plot useful in visualizing two-way interactions between predictor variables. Two of the predictor variables from the model are used to produce a grid of possible combinations of predictor values over the range of both variables. The remaining predictor variables from the model are fixed at either their means (for continuous predictors) or their most common value (for categorical predictors). Model predictions are generated over this grid and plotted as the z axis. This function works with both continuous and categorical predictors, though the perspective plot should be interpreted with care for categorical predictors. In particular, the smooth option is not appropriate if either of the two selected predictor variables is categorical. For categorical response models, a particular value must be specified for the response using the response.category argument.

References

This function is adapted from gbm.perspec version 2.9 April 2007, J Leathwick/J Elith. See appendix S3 from: Elith, J., Leathwick, J. R. and Hastie, T. (2008). A working guide to boosted regression trees. Journal of Animal Ecology. 77:802-813.

Examples

###########################################################################
############################# Run this set up code: #######################
###########################################################################

# set seed:
seed=38

# Define training and test files:

qdata.trainfn = system.file("external", "helpexamples","DATATRAIN.csv", package = "ModelMap")
qdata.testfn = system.file("external", "helpexamples","DATATEST.csv", package = "ModelMap")

# Define folder for all output:
folder=getwd()	

########## Continuous Response, Categorical Predictors ############


#file name to store model:
MODELfn="RF_BIO_TCandNLCD"			

#predictors:
predList=c("TCB","TCG","TCW","NLCD")

#define which predictors are categorical:
predFactor=c("NLCD")

# Response name and type:
response.name="BIO"
response.type="continuous"

#identifier for individual training and test data points

unique.rowname="ID"


###########################################################################
########################### build model: ##################################
###########################################################################


### create model ###

model.obj = model.build( model.type="RF",
                       qdata.trainfn=qdata.trainfn,
                       folder=folder,		
                       unique.rowname=unique.rowname,		
                       MODELfn=MODELfn,
                       predList=predList,
                       predFactor=predFactor,
                       response.name=response.name,
                       response.type=response.type,
                       seed=seed,
                       na.action=na.roughfix
)

###########################################################################
###################### make interaction plots: ############################
###########################################################################

#########################
### Perspective Plots ###
#########################


### specify first and third  predictors in 'predList (both continuous) ###

model.interaction.plot(	model.obj,
			x=1,y=3, 
			main=response.name, 
			plot.type="persp", 
			device.type="default") 

### specify first and forth predictors in 'predList (one continuous one factored) ###

model.interaction.plot(	model.obj,
			x=1, y=4, 
			main=response.name, 
			plot.type="persp", 
			device.type="default") 

### same as previous example, but specifying predictors by name ##

model.interaction.plot(	model.obj,
			x="TCB", y="NLCD",  
			main=response.name, 
			plot.type="persp", 
			device.type="default") 


###################
### Image Plots ###
###################

### same as previous example, but image plot ###


l <- seq(100,0,length.out=101)
c <- seq(0,100,length.out=101)
col.ramp <- hcl(h = 120, c = c, l = l)
 

model.interaction.plot(		model.obj,
				x="TCB", y="NLCD",
				main=response.name,
				plot.type="image", 
				device.type="default",
				col = col.ramp) 



#########################
### 3-way Interaction ###
#########################

### use 'pred.means' argument to fix values of additional predictors ###

### factored 3rd predictor ###

nlcd<-levels(model.obj$predictor.data$NLCD)

for(i in nlcd){
	pred.means=list(NLCD=i)

	model.interaction.plot(	model.obj,
				x="TCG", y="TCW",  
				main=paste("NLCD =",i),
				pred.means=pred.means, 
				z.range=c(0,110),
				theta=290,
				plot.type="persp", 
				device.type="default") 
}



### continuos 3rd predictor ###


tcb<-seq(	min(model.obj$predictor.data$TCB),
		max(model.obj$predictor.data$TCB),
		length=5)

tcb<-signif(tcb,2)

for(i in tcb){
	pred.means=list(TCB=i)

	model.interaction.plot(	model.obj,
				x="TCG", y="TCW",  
				main=paste("TCB =",i),
				pred.means=pred.means, 
				z.range=c(0,120),
				theta=290,
				plot.type="persp", 
				device.type="default") 
}



### 4-way Interesting combos ###


tcb=c(1300,2900,3400)
nlcd=c(11,90,95)

for(i in 1:3){
	pred.means=list(TCB=tcb[i],NLCD=nlcd[i])

	model.interaction.plot(	model.obj,
				x="TCG", y="TCW",  
				main=paste("TCB =",tcb[i],"NLCD =",nlcd[i]),
				pred.means=pred.means, 
				z.range=c(0,120),
				theta=290,
				plot.type="persp", 
				device.type="default") 
}