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PODisplaying text below the plot generated by ggplot2
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copied!<p>I am trying to display some information about the data below the plot created in <strong>ggplot2</strong>. I would like to plot the N variable using the X axis coordinate of the plot but the Y coordinate needs to be 10% from the bottom of the screen . In fact, the desired Y coordinates are already in the data frame as y_pos variable. </p> <p>I can think of 3 approaches using <strong>ggplot2</strong>:</p> <p>1) Create an empty plot below the actual plot, use the same scale and then use geom_text to plot the data over the blank plot. <a href="http://learnr.wordpress.com/2009/04/29/ggplot2-labelling-data-series-and-adding-a-data-table/" rel="nofollow noreferrer">This approach</a> sort of works but is extremely complicated.</p> <p>2) Use <code>geom_text</code> to plot the data but somehow use y coordinate as percent of the screen (10%). This would force the numbers to be displayed below the plot. I can't figure out the proper syntax. </p> <p>3) Use grid.text to display the text. I can easily set it at the 10% from the bottom of the screen but I can't figure how set the X coordindate to match the plot. I tried to use grconvert to capture the initial X position but could not get that to work as well.</p> <p>Below is the basic plot with the dummy data:</p> <pre><code>graphics.off() # close graphics windows library(car) library(ggplot2) #load ggplot library(gridExtra) #load Grid library(RGraphics) # support of the "R graphics" book, on CRAN #create dummy data test= data.frame( Group = c("A", "B", "A","B", "A", "B"), x = c(1 ,1,2,2,3,3 ), y = c(33,25,27,36,43,25), n=c(71,55,65,58,65,58), y_pos=c(9,6,9,6,9,6) ) #create ggplot p1 <- qplot(x, y, data=test, colour=Group) + ylab("Mean change from baseline") + geom_line()+ scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) + opts( legend.position=c(.1,0.9)) #display plot p1 </code></pre> <p>The modified gplot below displays numbers of subjects, however they are displayed WITHIN the plot. They force the Y scale to be extended. I would like to display these numbers BELOW the plot.</p> <pre><code> p1 <- qplot(x, y, data=test, colour=Group) + ylab("Mean change from baseline") + geom_line()+ scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) + opts( plot.margin = unit(c(0,2,2,1), "lines"), legend.position=c(.1,0.9))+ geom_text(data = test,aes(x=x,y=y_pos,label=n)) p1 </code></pre> <p>A different approach of displaying the numbers involves creating a dummy plot below the actual plot. Here is the code:</p> <pre><code>graphics.off() # close graphics windows library(car) library(ggplot2) #load ggplot library(gridExtra) #load Grid library(RGraphics) # support of the "R graphics" book, on CRAN #create dummy data test= data.frame( group = c("A", "B", "A","B", "A", "B"), x = c(1 ,1,2,2,3,3 ), y = c(33,25,27,36,43,25), n=c(71,55,65,58,65,58), y_pos=c(15,6,15,6,15,6) ) p1 <- qplot(x, y, data=test, colour=group) + ylab("Mean change from baseline") + opts(plot.margin = unit(c(1,2,-1,1), "lines")) + geom_line()+ scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) + opts(legend.position="bottom", legend.title=theme_blank(), title.text="Line plot using GGPLOT") p1 p2 <- qplot(x, y, data=test, geom="blank")+ ylab(" ")+ opts( plot.margin = unit(c(0,2,-2,1), "lines"), axis.line = theme_blank(), axis.ticks = theme_segment(colour = "white"), axis.text.x=theme_text(angle=-90,colour="white"), axis.text.y=theme_text(angle=-90,colour="white"), panel.background = theme_rect(fill = "transparent",colour = NA), panel.grid.minor = theme_blank(), panel.grid.major = theme_blank() )+ geom_text(data = test,aes(x=x,y=y_pos,label=n)) p2 grid.arrange(p1, p2, heights = c(8.5, 1.5), nrow=2 ) </code></pre> <p>However, that is very complicated and would be hard to modify for different data. Ideally, I'd like to be able to pass Y coordinates as percent of the screen.</p>

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