First of all, a practical way to supply data is to use the function dput()
Just do dput(mydata) and copy and paste the results into your email. The
reader can copy and paste into R and have an identical data set.
I am not sure I have followed exactly what you are doing but here is something
that may approach what you want, done using the ggp;pt2 package. Do
'install.packages("ggplot2) if you do not have it.
Anyway here is roughly your data set in the dput format
mydata <- structure(list(tradeflavor = c(1L, 2L, 1L, 1L, 1L, 2L, 16L, 1L,
16L, 1L, 1L, 16L, 1L, 4L, 8L, 1L, 8L, 16L, 1L, 8L, 16L, 1L, 4L,
8L, 16L, 1L, 2L, 4L, 8L, 1L, 4L, 8L, 16L, 1L, 2L, 4L, 8L, 16L,
1L, 2L), timestamp = structure(c(14266, 14266, 14267, 14271,
14272, 14272, 14272, 14273, 14273, 14274, 14277, 14277, 14278,
14278, 14278, 14279, 14279, 14279, 14280, 14280, 14280, 14281,
14281, 14281, 14281, 14284, 14284, 14284, 14284, 14285, 14285,
14285, 14285, 14286, 14286, 14286, 14286, 14286, 14287, 14287
), class = "Date"), x = c(1L, 1L, 1L, 54L, 105L, 2L, 2L, 71L,
2L, 42L, 19L, 2L, 36L, 2L, 3L, 73L, 12L, 7L, 53L, 6L, 9L, 38L,
6L, 2L, 3L, 42L, 2L, 1L, 2L, 87L, 2L, 4L, 3L, 55L, 6L, 4L, 2L,
8L, 153L, 6L)), .Names = c("tradeflavor", "timestamp", "x"), row.names = c(NA,
-40L), class = "data.frame")
#=====================================
library(ggplot2)
# first subset
m1data <- subset(mydata, tradeflavor == 1)
# plot for tradeflavor = 1
p1 <- ggplot(m1data , aes( timestamp, x)) + geom_point() +
geom_smooth(method = lm, se = FALSE)
p1
m2data <- subset(mydata, tradeflavor == 2)
p2 <- ggplot(m2data , aes( timestamp, x )) + geom_point() +
geom_smooth(method = lm, se = FALSE)
p2
# plot a grid of results
pgrid <- p <- ggplot(mydata , aes( timestamp, x)) + geom_point() +
geom_smooth(method = lm, se = FALSE) + facet_grid(tradeflavor ~ .)
pgrid
# Have fun with R.
John Kane
Kingston ON Canada
> -----Original Message-----
> From: norbert.skal...@ronin-capital.com
> Sent: Tue, 28 Aug 2012 11:48:32 -0500
> To: r-help@r-project.org
> Subject: [R] date in plot, can't add regression line
>
> Hello all,
>
> I have been using R for about 3 weeks and I am frustrated by a problem.
> I have read R in a nutshell, scoured the internet for help but I either
> am not understanding examples or am missing something completely basic.
> Here is the problem:
>
> I want to plot data that contains dates on the x axis. Then I want to
> fit a line to the data. I have been unable to do it.
>
> This is an example of the data (in a dataframe called
> "tradeflavorbyday"), 40 lines of it (I'm sorry it's not in a runnable
> form, not sure how to get that from R) :
> tradeflavor timestamp x
> 1 1 2009-01-22 1
> 2 2 2009-01-22 1
> 3 1 2009-01-23 1
> 4 1 2009-01-27 54
> 5 1 2009-01-28 105
> 6 2 2009-01-28 2
> 7 16 2009-01-28 2
> 8 1 2009-01-29 71
> 9 16 2009-01-29 2
> 10 1 2009-01-30 42
> 11 1 2009-02-02 19
> 12 16 2009-02-02 2
> 13 1 2009-02-03 36
> 14 4 2009-02-03 2
> 15 8 2009-02-03 3
> 16 1 2009-02-04 73
> 17 8 2009-02-04 12
> 18 16 2009-02-04 7
> 19 1 2009-02-05 53
> 20 8 2009-02-05 6
> 21 16 2009-02-05 9
> 22 1 2009-02-06 38
> 23 4 2009-02-06 6
> 24 8 2009-02-06 2
> 25 16 2009-02-06 3
> 26 1 2009-02-09 42
> 27 2 2009-02-09 2
> 28 4 2009-02-09 1
> 29 8 2009-02-09 2
> 30 1 2009-02-10 87
> 31 4 2009-02-10 2
> 32 8 2009-02-10 4
> 33 16 2009-02-10 3
> 34 1 2009-02-11 55
> 35 2 2009-02-11 6
> 36 4 2009-02-11 4
> 37 8 2009-02-11 2
> 38 16 2009-02-11 8
> 39 1 2009-02-12 153
> 40 2 2009-02-12 6
>
>
> The plot displays the x column as the yaxis and the date as the x axis,
> grouped by the tradetype column.
> The timestamp column:
>> class(tradeflavorbyday$timestamp)
> [1] "POSIXlt" "POSIXt"
>
> So in this case I want to plot tradetype 1 (method 1):
>
> xdates <- tradeflavorbyday$timestamp[tradeflavorbyday$tradeflavor == 1]
> ydata <- tradeflavorbyday$x[tradeflavorbyday$tradeflavor == 1]
>
> plot(xdates, ydata, col="black", xlab="Dates", ylab="Count")
>
> Up to here it works great.
>
> Now a abline through lm:
>
> xylm <- lm(ydata~xdates) <------ this fails, can't do dates as below
> abline(xylm, col="black")
>
>> lm(ydata~xdates)
> Error in model.frame.default(formula = ydata ~ xdates, drop.unused.levels
> = TRUE) :
> invalid type (list) for variable 'xdates'
>
>
>
> So I try this instead (method 2):
> xdata <- 1:length(tradeflavorbyday$timestamp[tradeflavorbyday$tradeflavor
> == 1])
> ydata <- tradeflavorbyday$x[tradeflavorbyday$tradeflavor == 1]
>
> xylm <- lm(ydata~xdata) <------ now this works, great
> abline(xylm, col="black")
>
> The problem now is that I can't get the dates onto the xaxis. I have
> tried turning off the axis using xaxt="n" and reploting using the
> axis.POSIXct() call but it does not want to display the dates:
>
> dateseq = seq(xdates[1], xdates[length(xdates)], by="month")
> axis.POSIXct(1, at=dateseq, format="%Y\n%b")
>
>
>
>
> I have tried combining both approaches by plotting dates and trying to
> fit the line using method 2:
> xdates <- tradeflavorbyday$timestamp[tradeflavorbyday$tradeflavor == 1]
> xdata <- 1:length(tradeflavorbyday$timestamp[tradeflavorbyday$tradeflavor
> == 1])
> ydata <- tradeflavorbyday$x[tradeflavorbyday$tradeflavor == 1]
>
> plot(xdates, ydata, col="black", xlab="Dates", ylab="Count", xaxt="n")
> dateseq = seq(xdates[1], xdates[length(xdates)], by="month")
> axis.POSIXct(1, at=dateseq, format="%Y\n%b")
>
> xylm <- lm(ydata~xdata) <- works
> abline(xylm, col="black") <- does nothing
>
> In this case the call to lm and abline "works" but nothing is drawn.
> Confused I plugged in the coefficients manually (I have complete data, so
> they will be different than the example data I pasted):
>
>> lm(ydata~xdata)
>
> Call:
> lm(formula = ydata ~ xdata)
>
> Coefficients:
> (Intercept) xdata
> 6.11491 -0.02577
>
> Abline(6.11491, -0.02577) <- call worked, but nothing shown
>
> Just by chance I added many 0 to flatten out the slope:
>
> Abline(6.11491, -0. 0000000002577) <- call worked and a horizontal line
> appeared?????
>
> So I took off a 0:
>
> Abline(6.11491, -0. 000000002577) <- the line moved significantly down
>
> So I took off another 0:
>
> Abline(6.11491, -0. 00000002577) <- line disappeared
>
> I guess the slope causes it to go vertical and disappear of the graph.
>
> I have no idea how to solve my issue. If anyone can see my basic idiotic
> error please point it out, or maybe you have another suggestion, I will
> gladly try it.
>
> Thanks for your help!!
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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