Changing tick intervals when x axis values are dates
Apologies if this is easy to solve, but I can't get my head around it.
I have this data frame:
> aaci
Date Plate.1 Plate.2 Plate.3 Plate.4 Plate.5 Plate.6 Plate.7 Plate.8 Average SE Species
1 2014-06-19 0.0000000 0.0000000 0.000000 0.000000 0.0000000 0.0000000 0.000000 0.0000000 0.000000 0.0000000 aa
7 2014-08-04 7.0057778 11.0000000 24.269333 10.439111 28.5724444 92.4604444 5.584000 55.5448889 29.359500 10.7354126 aa
13 2014-09-17 84.4075556 59.2493333 62.664444 38.147556 73.8417778 93.5208889 72.782667 94.5164444 72.391333 6.7116450 aa
19 2014-10-16 56.9840000 64.9733333 45.124444 38.817333 56.2031111 76.4613333 NA 85.4017778 60.566476 6.2339579 aa
25 2014-11-14 75.7146667 72.3604444 62.126222 20.095111 73.9520000 83.8688889 NA 61.5466667 64.237714 7.9248240 aa
31 2014-12-12 61.6942222 65.4386667 46.337778 20.824444 NA 92.4413333 NA 76.3115556 60.508000 10.1172930 aa
37 2015-02-12 63.0524444 79.3906667 70.264444 15.057778 NA 105.0115556 NA 77.2866667 68.343926 12.1348258 aa
43 2015-03-09 72.0408889 59.5875556 68.546222 12.160444 NA 84.2777778 NA 70.9191111 61.255333 10.3376277 aa
2 2014-06-19 0.0000000 0.0000000 0.000000 0.000000 0.0000000 0.0000000 0.000000 0.0000000 0.000000 0.0000000 ci
8 2014-08-04 2.6173333 2.3884444 1.532889 0.000000 0.8017778 0.0000000 0.000000 0.9026667 1.030389 0.3748546 ci
14 2014-09-17 0.6782222 0.9875556 2.130222 2.372889 2.2395556 0.8448889 4.001333 0.1568889 1.676444 0.4408737 ci
20 2014-10-16 7.8302222 0.9142222 1.550222 1.792444 1.8346667 0.0000000 NA 0.0000000 1.988825 1.0170247 ci
26 2014-11-14 6.9600000 1.2528889 1.005778 6.876444 4.8715556 1.0506667 NA 10.3613333 4.625524 1.3864420 ci
32 2014-12-12 13.7844444 1.9368889 2.971556 10.785778 NA 1.5231111 NA 5.1284444 6.021704 2.0815131 ci
38 2015-02-12 3.4862222 3.9262222 1.613333 10.524444 NA 2.2493333 NA 3.6991111 4.249778 1.3078608 ci
44 2015-03-09 5.1493333 5.1004444 6.648000 14.676889 NA 9.3968889 NA 9.7488889 8.453407 1.4912960 ci
I am using this code to produce a plot:
ggplot(aaci, aes(x=Date, y=Average, colour=Species)) +
geom_point(aes(colour=Species), size=4) +
geom_line(aes(colour=Species), size=1.3) +
geom_errorbar(aes(ymin=Average-SE, ymax=Average+SE),
size = .7,
width=8, colour="black",
position = position_dodge(.9)) +
scale_y_continuous(limits = c(0,100), breaks=seq(0,100,10)) +
labs(x=("Date of Panel Observation"), y=("Mean Cover (%)")) +
scale_colour_manual(values = colz, breaks = c("aa", "ci"),labels=c(expression(italic('Ascidiella aspersa')), expression(italic('Ciona intestinalis')))) +
theme_bw() +
theme(panel.background = element_rect(colour = "black"),
axis.text=element_text(size=14),
axis.title.x = element_text(vjust=-0.2),
axis.title.y = element_text(vjust=+0.6),
axis.title=element_text(size=16,face="bold"),
legend.justification = c(1, 1), legend.position = c(1, 1),
legend.title=element_text(size=14),
legend.text=element_text(size=12))
I have been trying to alter the x axis tick intervals to every month, to read: July, August, September, October, November, December, January, February, March. As you can see I have succesfully manually edited my y axis. I have read many posts on changing x axis ticks but I can't seem to find a solution to my particular problem. Any assistance would be greatly appreciated.
Answer
Upgrade comment
You can change the x-axis labels using scale_x_date and formats from the scales package. Using the code from the ggplot2 scale_x_date help pages
library(ggplot2)
library(scales) # to access breaks/formatting functions
# Change Date to date format
aaci$dt <- as.Date(aaci$Date)
# Plot
# You can change the format to suit your requirements
ggplot(aaci, aes(x=dt, y=Average, colour=Species, group=Species)) +
geom_point(size=4) +
geom_line(size=1.3) +
scale_y_continuous(limits = c(0,100), breaks=seq(0,100,10)) +
scale_x_date(date_breaks = "months" , date_labels = "%b-%y")
