Plot with dates as X axis in R - r

Question

I maintain my journal electronically and I'm trying to get an idea of how consistent I've been with my journal writing over the last few months. I have the following data file, which shows how many journal entries (Entry Count) and words (Word Count) I recorded over the preceding 30-day period.
Date Entry Count Word Count
2010-08-25 22 4205
2010-08-26 21 4012
2010-08-27 20 3865
2010-08-28 20 4062
2010-08-29 19 3938
2010-08-30 18 3759
2010-08-31 17 3564
2010-09-01 17 3564
2010-09-02 16 3444
2010-09-03 17 3647
2010-09-04 17 3617
2010-09-05 16 3390
2010-09-06 15 3251
2010-09-07 15 3186
2010-09-08 15 3186
2010-09-09 16 3414
2010-09-10 15 3228
2010-09-11 14 3006
2010-09-12 13 2769
2010-09-13 13 2781
2010-09-14 12 2637
2010-09-15 13 2774
2010-09-16 13 2808
2010-09-17 12 2732
2010-09-18 12 2664
2010-09-19 13 2931
2010-09-20 13 2751
2010-09-21 13 2710
2010-09-22 14 2950
2010-09-23 14 2834
2010-09-24 14 2834
2010-09-25 14 2834
2010-09-26 14 2834
2010-09-27 14 2834
2010-09-28 14 2543
2010-09-29 14 2543
2010-09-30 15 2884
2010-10-01 16 3105
2010-10-02 16 3105
2010-10-03 16 3105
2010-10-04 15 2902
2010-10-05 14 2805
2010-10-06 14 2805
2010-10-07 14 2805
2010-10-08 14 2812
2010-10-09 15 2895
2010-10-10 14 2667
2010-10-11 15 2876
2010-10-12 16 2938
2010-10-13 17 3112
2010-10-14 16 2894
2010-10-15 16 2894
2010-10-16 16 2923
2010-10-17 15 2722
2010-10-18 15 2722
2010-10-19 14 2544
2010-10-20 13 2277
2010-10-21 13 2329
2010-10-22 12 2132
2010-10-23 11 1892
2010-10-24 10 1764
2010-10-25 10 1764
2010-10-26 10 1764
2010-10-27 10 1764
2010-10-28 10 1764
2010-10-29 9 1670
2010-10-30 10 1969
2010-10-31 10 1709
2010-11-01 10 1624
2010-11-02 11 1677
2010-11-03 11 1677
2010-11-04 11 1677
2010-11-05 11 1677
2010-11-06 12 1786
2010-11-07 12 1786
2010-11-08 11 1529
2010-11-09 10 1446
2010-11-10 11 1682
2010-11-11 11 1540
2010-11-12 11 1673
2010-11-13 11 1765
2010-11-14 12 1924
2010-11-15 13 2276
2010-11-16 12 2110
2010-11-17 13 2524
2010-11-18 14 2615
2010-11-19 14 2615
2010-11-20 15 2706
2010-11-21 14 2549
2010-11-22 15 2647
2010-11-23 16 2874
2010-11-24 16 2874
2010-11-25 16 2874
2010-11-26 17 3249
2010-11-27 18 3421
2010-11-28 18 3421
2010-11-29 19 3647
I'm trying to plot this data with R to get a graphical representation of my journal-writing consistency. I load it into R with the following command.
d <- read.table("journal.txt", header=T, sep="\t")
I can then graph the data with the following command.
plot(seq(from=1, to=length(d$Entry.Count), by=1), d$Entry.Count, type="o", ylim=c(0, max(d$Entry.Count)))
However, in this plot the X axis is just a number, not a date. I tried adjusting the command to show dates on the X axis like this.
plot(d$Date, d$Entry.Count, type="o", ylim=c(0, max(d$Entry.Count)))
However, not only does the plot look strange, but the labels on the X axis are not very helpful. What is the best way to plot this data so that I can clearly associate dates with points on the plotted curve?

Answer 1

Based on your code the dates are just characters.
Try converting them to Dates:
plot(as.Date(d$Date), d$Entry.Count)
Quite simple in your case as the "%Y-%m-%d" format is the default for as.Date. See strptime for more general options.

Answer 2

You could use zoo. ?plot.zoo has several examples of how to create custom axis labels.
z <- zoo(d[,-1],as.Date(d[,1]))
plot(z)
# Example of custom axis labels
plot(z$Entry.Count, screen = 1, col = 1:2, xaxt = "n")
ix <- seq(1, length(time(z)), 3)
axis(1, at = time(z)[ix], labels = format(time(z)[ix],"%b-%d"), cex.axis = 0.7)