basicTrendline (version 1.0.1)

trendline: Add Trendline and Show Equation to Plot

Description

Plot and show both regression line and equation as simple as possible, by using different models built in the 'trendline()' function. The function includes the following models in the latest version: "line2P" (formula as: y=a*x+b), "line3P" (y=a*x^2+b*x+c), "log2P" (y=a*ln(x)+b), "exp3P" (y=a*exp(b*x)+c), and "power3P" (y=a*x^b+c). Besides, the summarized results of each fitted model are also output by default.

Usage

trendline(x, y, model = "line2P", plot = TRUE, linecolor = "red",
  lty = 1, lwd = 1, summary = TRUE, ePos = "topleft", eDigit = 5,
  eSize = 1)

Arguments

x, y

the x and y arguments provide the x and y coordinates for the plot. Any reasonable way of defining the coordinates is acceptable.

model

select which model to fit. Default is "line2P". The "model" should be one of c("line2P", "line3P", "log2P", "exp3P", "power3P"), their formulas are as follows: "line2P": y=a*x+b "line3P": y=a*x^2+b*x+c "log2P": y=a*ln(x)+b "exp3P": y=a*exp(b*x)+c "power3P": y=a*x^b+c

plot

draw a scatter plot automatically, the vlaue is one of c("TRUE", "FALSE").

linecolor

color of regression line.

lty

line type. lty can be specified using either text c("blank","solid","dashed","dotted","dotdash","longdash","twodash") or number c(0, 1, 2, 3, 4, 5, 6). Note that lty = "solid" is identical to lty=1.

lwd

line width. Default is 1.

summary

summarizing the model fits. Default is TRUE.

ePos

equation position, such as one of c("none","bottomright","bottom","bottomleft","left","topleft","top","topright","right","center").

eDigit

the numbers of digits for equation parameters. Default is 5.

eSize

font size in percentage of equation. Default is 1.

Value

R^2, indicates the R-Squared value of each regression model.

p, indicates the p-value of each regression model.

AIC or BIC, indicate the Akaike's Information Criterion or Bayesian Information Criterion for fitted model. Click AIC for details. The smaller the AIC or BIC, the better the model.

See Also

trendline, SSexp3P, SSpower3P, nls, selfStart

Examples

# NOT RUN {
library(basicTrendline)
x1<-1:5
x2<- -2:2
x3<- c(101,105,140,200,660)
x4<- -5:-1
x5<- c(1,30,90,180,360)

y1<-c(2,14,18,19,20)        # increasing convex trend
y2<- c(-2,-14,-18,-19,-20)  # decreasing concave trend
y3<-c(2,4,16,38,89)         # increasing concave trend
y4<-c(-2,-4,-16,-38,-89)    # decreasing convex trend
y5<- c(600002,600014,600018,600019,600020) # high y values with low range.

trendline(x1,y1,model="line2P",summary=TRUE,eDigit=10)
trendline(x2,y2,model="line3P",summary=FALSE,ePos="topright")
trendline(x3,y3,model="log2P",linecolor="blue")
trendline(x4,y4,model="exp3P",eSize=0.7) #change the font size of equation.
trendline(x5,y5,model="power3P")

## Not run
plot(x1,y1,main="Different regression lines in one plot")
library(basicTrendline)
trendline(x1,y1,model="line2P",plot=FALSE,ePos="none",linecolor="red")
trendline(x1,y1,model="log2P",plot=FALSE,ePos="none",linecolor="blue",lty=2)
trendline(x1,y1,model="exp3P",plot=FALSE,ePos="none",linecolor="black",lty=3)
legend("bottomright",c("line2P","log2P","exp3P"), lty=c(1,2,3),col=c("red","blue","black"))
## END (Not run)

# }