data_USDA {ggtern}

USDA Textural Classification Data

Description

This dataset was issued by the United States Department of Agriculture (USDA) in the form of a ternary diagram, this original ternary diagram has been converted to numerical data and included here.

Usage

data(USDA)

Format

1row per point, many points per classification representing the extremes of the area.

Author(s)

United States Department of Agriculture (USDA)

Nicholas Hamilton

Source

Soil Mechanics Level 1, Module 3, USDA Textural Classification Study Guide

See Also

ggtern datasets

Examples

#Load the Libraries
library(ggtern)
library(plyr)

#Load the Data.
data(USDA)

#Put tile labels at the midpoint of each tile.
USDA.LAB <- ddply(USDA,"Label",function(df){
  apply(df[,1:3],2,mean)
})

#Tweak
USDA.LAB$Angle = sapply(as.character(USDA.LAB$Label),function(x){
    switch(x,"Loamy Sand"=-35,0)
})

#Construct the plot.
ggtern(data=USDA,aes(Sand,Clay,Silt,color=Label,fill=Label)) +
  geom_polygon(alpha=0.75,size=0.5,color="black") +
  geom_mask() +  
  geom_text(data=USDA.LAB,aes(label=Label,angle=Angle),color="black",size=3.5) +
  theme_rgbw() + 
  theme_showsecondary() +
  theme_showarrows() +
  weight_percent() + 
  guides(fill='none') + 
  theme_legend_position("topleft") + 
  labs(title = "USDA Textural Classification Chart",
       fill  = "Textural Class",
       color = "Textural Class")