我有两组数据（3列：x=分类，y=数值，l=位置），我想创建一个条形图，x轴上为类别，并且对于每个类别的值，使用不同颜色的两个垂直条形图，显示每个位置的y值。默认情况下，Excel/OpenOffice会生成这种类型的图表。
我尝试过
qplot (x,y,data=mydata,col=location, geom="histogram")
但它生成的是堆叠条形图，而不是并排的。然后我查看了ggplot2文档，并没有找到其他可用的几何对象（请参见下面的完整列表）。
使用ggplot2不可能实现这个吗？
提前致谢。
Name Description
abline - Line, specified by slope and intercept
area - Area plots
bar - Bars, rectangles with bases on y-axis
blank - Blank, draws nothing
boxplot - Box-and-whisker plot
contour - Display contours of a 3d surface in 2d
crossbar - Hollow bar with middle indicated by horizontal line
density - Display a smooth density estimate
density_2d - Contours from a 2d density estimate
errorbar - Error bars
histogram - Histogram
hline - Line, horizontal
interval - Base for all interval (range) geoms
jitter - Points, jittered to reduce overplotting
line - Connect observations, in order of x value
linerange - An interval represented by a vertical line
path - Connect observations, in original order
point - Points, as for a scatterplot
pointrange - An interval represented by a vertical line, with a point
in the middle
polygon - Polygon, a filled path
quantile - Add quantile lines from a quantile regression
ribbon - Ribbons, y range with continuous x values
rug - Marginal rug plots
segment - Single line segments
smooth - Add a smoothed condition mean
step - Connect observations by stairs
text - Textual annotations
tile - Tile plot as densely as possible, assuming that every tile is the same size
vline - Line, vertical