Plot multiple similar equations in r

On 2 Mar 2016, at 22:22, David L Carlson <dcarlson at tamu.edu> wrote:

Another way would be to use matplot() or matlines():

lx<-c(0.4, 0.5, 0.6, 0.7)
x <- seq(1, 8, length.out=100)
myfun <- function(x, k) {(log(k)-(0.37273*log(x)-1.79389))/0.17941}
y <- sapply(lx, function(k) myfun(x, k))
matplot(x, a, type="l", col="black", lty=1)

-

------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Dalthorp, Daniel
Sent: Wednesday, March 2, 2016 1:05 PM
To: Jinggaofu Shi
Cc: r-help at R-project.org (r-help at r-project.org)
Subject: Re: [R] Plot multiple similar equations in r

Or, if you want easy labels, you can play around with contour graphs.

?contour # will give you info on how to make contour plots

The basic idea is to construct a matrix of z-values...one z for every
combination of x and y
contour(x,y,z)

The x's would then be the x-values you want in
(0.37273*log(x)-1.79389))/0.17941 for whatever range of x's you want
The y's would be values from -5 to 5 (or whatever range you want)
The z's would be values like 0.4, 0.5, etc. or exp(y + x)

?outer # will tell you how to create z from x and y

x<-seq(1,10,length=100) # values for x-axis
y<-seq(2, 10, length=100) # values for y-axis
z<-exp(outer((0.37273*log(x)-1.79389)/0.17941,y,"+"))
contour(x,y,z,levels=seq(.1,1.1,by=.1))

-Dan

On Wed, Mar 2, 2016 at 9:03 AM, Jinggaofu Shi <js3786 at drexel.edu> wrote:

Hi, there I am new on R. I want to plot a graph like this.

The curves are created by these equations :
(log(0.4)-(0.37273*log(x)-1.79389))/0.17941,
(log(0.5)-(0.37273*log(x)-1.79389))/0.17941,
(log(0.6)-(0.37273*log(x)-1.79389))/0.17941, etc. The equations are
similar, the only difference is the first log(XXX). I already manually draw
the graph by repeating plot() for each equation. But I think there must be
a way to just assign a simple variable like x<-c(0.4,0.5,0.6,0.7), and then
plot all the curves automatically. I tried to use data frame to make a set
of equations, but failed. Could somebody help me? Thank you very much!

-- 
Dan Dalthorp, PhD
USGS Forest and Rangeland Ecosystem Science Center
Forest Sciences Lab, Rm 189
3200 SW Jefferson Way
Corvallis, OR 97331
ph: 541-750-0953
ddalthorp at usgs.gov

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