Steve,
This is on the edge of what R-sig-teaching is for (since it isn’t really about
teaching). But since I think there are elements of what you are doing that
lead students to think that R is terrible, I’ll show you how I might approach
things.
First a few comments about my solution.
1) I generally avoid loose vectors. I prefer to use data frames to keep
related vectors related.
2) I prefer to code dates as dates. I would be very nervous about code that
manually sets the axis labels differently from the data. That can lead to all
sorts of bad errors down the road if you change the data and forget to change
the labels and often indicates you don’t have the data formatted the way you
should. (Note: I added day of month values to your dates that had none.) The
lubridate package makes it easy to create dates from strings.
3) I rarely use base graphics, so I’ll show you solutions using lattice and
ggplot2. There may be nice ways to do this in base graphics as well.
4) I’m ignoring the color choices, title, etc. All that can be easily added,
but I’m focusing on getting the data display correct. That’s generally the
approach I take to plotting: First get the data display correct, then fancy up
titles, colors, fonts, etc. It’s saves lots of times, because often once I see
the plot, I realize it isn’t what I need, so there is no reason to gussy it up.
5) I prefer (and lattice and ggplot2) encourage keeping the data manipulation
in one location and the plotting after that rather than going back and forth
between those two types of operations. I find that it makes the code easier to
read.
6) One of your series as fewer points than the other. I made the assumption
that the missing value was at the end. That should be changed to whatever is
correct for your data.
7) I don’t know what you were using pch to indicate, so I created a variable
called “group” with values 0 and 15. The variable and its values should
ideally be renamed to reflect what they represent. That will make your code
easier to read and produce better labeling of the plot.
And one note about your code.
6*0:max_y
probably doesn’t do what you expect since the 6 does nothing here (because 6 *
0 = 0). You could do 6 * (0:max_y), but isn’t clear why you would want the
range of the plot to be six times that of the data. Maybe you were thinking
something like seq(0, max_y, length.out = 6), but that will give pretty ugly
breakpoints. In any case, the plots below do a fine job of setting the axes by
default, and each system allows you to tune them if you disagree with the
default for a particular plot.
With that much preamble, the code is now shorter than the introduction.
### Put data into a data frame -- avoid loose vectors
library(dplyr); library(lubridate)
# if i knew what you were using pch for, i would name group and its values to
match
MyData <- data_frame(
Well1 =
c(0.005,0.005,0.004,0.006,0.004,0.009,0.017,0.045,0.05,0.07,0.12,0.10,0.20,0.25),
Well2 =
c(0.10,0.12,0.125,0.107,0.099,0.11,0.13,0.109,0.10,0.115,0.14,0.17,0.11,NA),
dateString =
c("1Jan05","1April05","1Jul05","1Oct05","1Jan06","1March06","1Jun06","2Oct06","17Oct06","1Jan07","1April07","1Jul07","1Oct07","1Dec07"),
date = dmy(dateString),
group = factor(c(0,0,15,15,0,15,15,15,15,15,15,15,15,15))
)
## using lattice
## lattice makes plotting two series easy
## but doesn't make it as easy to have different symbols along the same series
library(lattice)
xyplot(Well1 + Well2 ~ date, data = MyData, type = c("p","l"), auto.key = TRUE)
## better legend
xyplot(Well1 + Well2 ~ date, data = MyData, type = c("p","l"),
auto.key = list(points = TRUE, lines = TRUE))
## using ggplot2
## for highly customized plots, i generally find ggplot2 works better
## i would reshape the data with tidyr before plotting (could be don in lattice
as well)
library(ggplot2); library(tidyr)
MyData2 <-
MyData %>%
gather(location, concentration, Well1, Well2)
ggplot( data = MyData2, aes(x = date, y = concentration, colour = location)) +
geom_line() +
geom_point( aes(shape = group), size = 2)
xyplot(concentration ~ date, data = MyData2, groups = location, type = c("p",
"l"),
auto.key = TRUE)
## without reshaping, you can plot 4 layers well manually, but the default
labeling isn’t as nice
ggplot(data = MyData) +
geom_line(aes(x = date, y = Well1, colour = "Well1")) +
geom_line(aes(x = date, y = Well2, colour = "Well2")) +
geom_point(aes(x = date, y = Well1, colour = "Well1", shape = group)) +
geom_point(aes(x = date, y = Well2, colour = "Well2", shape = group))
Happy Holidays. I hope one of these approaches will get you headed in the
right direction.
—rjp
On Dec 24, 2015, at 7:51 AM, Steven Stoline
<sstol...@gmail.com<mailto:sstol...@gmail.com>> wrote:
Dear All:
I am trying to plot two series in one graph. But I have some difficulties
to set up the y-axis lim. Also, the second series is not correctly graphed.
*Here is what I tried to do:*
### Define 2 vectors
Well1<-c(0.005,0.005,0.004,0.006,0.004,0.009,0.017,0.045,0.05,0.07,0.12,0.10,0.20,0.25)
Well2<-c(0.10,0.12,0.125,0.107,0.099,0.11,0.13,0.109,0.10,0.115,0.14,0.17,0.11)
### Calculate range from 0 to max value of Well1 and Well2
### g_range <- range(0, Well1, Well2)
max_y <- max(Well1, Well2)
### Graph Groundwater Concentrations using y axis that ranges from 0 to max
### value in Well1 or Well2 vector. Turn off axes and
### annotations (axis labels) so we can specify them yourself
plot(Well1, type="o", pch=c(0,0,15,15,0,15,15,15,15,15,15,15,15,15),
col="blue", ylim=c(0,max_y), axes=FALSE, ann=FALSE, , lwd=3, cex=1.25) ###
axes=FALSE,
### Make x axis using Jan 2005 - Dec 2008 labels
axis(1, at=1:14,
lab=c("Jan05","April05","Jul05","Oct05","Jan06","March06","Jun06","2Oct06","17Oct06","Jan07","April07","Jul07","Oct07","Dec07"))
*### Make y axis with horizontal labels , Here what I have the major
problem*
### I want the y-axis looks like: 0, 0.05, 0.10, 0.15, 20, 0.25
axis(2, las=0, at=6*0:max_y) ### max_y
### Create box around plot
box()
### Graph Well2 with red dashed line and square points
### lines(Well2, type="o", pch=22, lty=2, col="red", lwd=3, cex=1.0)
lines(Well2, type="o", pch=c(0,15,15,15,0,15,15,15,0,15,15,15,15), lty=2,
col="red", lwd=3, cex=1.25)
### Create a title with a red, bold/italic font
title(main="Trichloroethene mg/L from Wells 1 and 2 - 2005-2007",
col.main="red", font.main=2)
### Label the x and y axes with dark green text
title(xlab="Time Points", col.lab=rgb(0,0.5,0))
title(ylab="Trichloroethene mg/L", col.lab=rgb(0,0.5,0))
### Create a legend
legend(1, g_range[2], c("Well1","Well2"), cex=1.0, col=c("blue","red"),
pch=15:15, lty=1:2);
with thanks
steve
-------------------------
Steven M. Stoline
1123 Forest Avenue
Portland, ME 04112
sstol...@gmail.com<mailto:sstol...@gmail.com>
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