If statement 使用if-else参数绘制多个因子

我希望每次在两个不同的图中绘制我的数据，一个用于前数据，一个用于后数据，在每个图中，

x

轴表示子id，

Y

轴表示响应错误。我希望数据按分组系数分组

我试过以下方法

    mytheme3 <- theme(legend.text = element_text(face = "italic",colour="black",
                                         family = "Helvetica", size = rel(1)), 
              axis.title = element_text(colour="black",family = "black",
                                        size = rel(1)), 
              axis.text = element_text(family = "black",colour = "black",
                                       size = rel(1)), 
              axis.line = element_line(size = 1,colour = "black"), 
              axis.ticks = element_line(colour="grey",size = rel(1)),
              # panel.grid.major = element_line(colour="grey",size = rel(0.5)), 
              # panel.grid.minor = element_blank(), 
              panel.background = element_rect(fill = "white"), 
              legend.key = element_rect(fill = "white"), 
              legend.title = element_text(colour = "steelblue",size = rel(1),
                                          family = "Helvetica"), 
              plot.title = element_text(colour = "steelblue4", face = "bold",
                                        size = rel(1.5),family = "Helvetica"))


    if (mazeData$Session == "Session1" & mazeData$Condition == "SR") {

    plot1<-ggplot(mazeData, aes(Errorfixed,SubjectID,colour=Group))+geom_point() + mytheme3+ 
    ggtitle("Error for test1") + labs(y = "Subject ID", x = "Error (degrees)", colour = "Group") + 
   scale_colour_manual(values = c("deeppink", "blue", "black"))
    } else if (mazeData$Session == 'Session2' & mazeData$Condition == 'SR') {

     plot2<-ggplot(mazeData, aes(Errorfixed,SubjectID,colour = Group))+geom_point() + mytheme3+ 
    ggtitle("Error for test2") + labs(y="Subject ID", x = "Error (degrees)", colour = "Group") + 
    scale_colour_manual(values = c("deeppink", "blue", "black"))

    }
   ggplot2.multiplot (plot1, plot2, cols = 2)

如何将我的因子矢量化？还是解决这个错误

    Warning messages:
    1: In if (mazeData$Session == "Session1" & mazeData$Condition == "SR") { :
    the condition has length > 1 and only the first element will be used
   2: In if (mazeData$Session == "Session2" & mazeData$Condition == "SR") { :
    the condition has length > 1 and only the first element will be used