r - Draw several plots at specified coordinates using annotation_custom() -

i want place ggplot graphs in specified locations on map. chose ggplot2 package because i'm more familiar grid. if me small example how use grid such task, appreciate such answer well.

here simple example:

# create base plot g <- ggplot(data.frame(x=c(-104,-94), y=c(33,38)), aes(x=x, y=y)) +    geom_blank()  # create theme tm <- theme(axis.title = element_blank(),             axis.text = element_blank(),             axis.ticks = element_blank(),             axis.line = element_blank(),             panel.background = element_blank(),             panel.grid = element_blank(),             panel.border = element_rect(color="grey", fill=na),             title = element_text(size=5))  # create 2 plot should placed on base plot p1 <- ggplot(data.frame(x=c(-104,-94), y=c(33,38)), aes(x=x, y=y)) +    geom_point() + tm p2 <- ggplot(data.frame(x=c(-100,-98), y=c(34,37)), aes(x=x, y=y)) +    geom_point() + tm  # place them using annotation_custom() function a1 <- annotation_custom(grob = ggplotgrob(p1),                          xmin = -104, xmax = -102,                         ymin = 33, ymax = 35) a2 <- annotation_custom(grob = ggplotgrob(p2),                          xmin = -100, xmax = -98,                         ymin = 35, ymax = 37)  # draw g + a1 g + a2 g + a1 + a2 

but in case of g + a1 + a2 obtain first picture first plot p1 inserted. what's wrong? how draw 2 , more plots using annotation_custom()?

it's weird bug noticed recently; grobs ggplot2 considers similar, position can ignored , end superposed:

mygrob <- rectgrob(gp=gpar(fill="red", alpha=0.5), name="whatever") mygrob2 <- rectgrob(gp=gpar(fill="blue", alpha=0.5))  # fine qplot(1:10, 1:10) + theme(plot.margin=unit(c(0, 3, 0, 0), "cm")) +   annotation_custom(mygrob, xmin=5, xmax=6, ymin=3.5, ymax=5.5) +   annotation_custom(mygrob2, xmin=8, xmax=12, ymin=3.5, ymax=5.5)   # using twice same grob, sit on top of each other p <- qplot(1:10, 1:10) + theme(plot.margin=unit(c(0, 3, 0, 0), "cm")) +   annotation_custom(mygrob, xmin=5, xmax=6, ymin=3.5, ymax=5.5) +   annotation_custom(mygrob, xmin=8, xmax=12, ymin=3.5, ymax=5.5)   g <- ggplotgrob(p) grid.ls(g$grobs[[4]]) # 2 of them 

i have no idea what's causing this, presumably it's related problem.