facet_grid和facet_wrap更改百分比时的轴比例

Question

我想绘制每年的直方图，但是当我使用facet_grid或facet_wrap时，y轴变化的百分比。 您可以从here下载数据。

正常使用：

<VBox prefHeight="400.0" prefWidth="600.0">
   <children>
      <HBox style="-fx-background-color: green;" VBox.vgrow="SOMETIMES" />
      <HBox style="-fx-background-color: blue;" VBox.vgrow="SOMETIMES" />
      <HBox style="-fx-background-color: red;" VBox.vgrow="SOMETIMES" />
   </children>
</VBox>

方面：

<VBox fx:id="vbox" fillWidth="false" prefHeight="400.0" prefWidth="600.0">
   <children>
      <HBox prefHeight="100.0" style="-fx-background-color: green;" VBox.vgrow="SOMETIMES" prefWidth="${vbox.width * 0.5}" />
      <HBox prefHeight="100.0" style="-fx-background-color: blue;" VBox.vgrow="SOMETIMES" prefWidth="${vbox.width * 0.5}" />
      <HBox prefHeight="100.0" style="-fx-background-color: red;" VBox.vgrow="SOMETIMES" prefWidth="${vbox.width * 0.5}" />
   </children>
</VBox>

使用data <- gss %>% select(year, educ, race) %>% filter(race!="Other", year %in% 1972:1977) ggplot(data %>% filter(year == 1972)) + geom_histogram(data = data %>% filter(race=="Black"), aes(y=(..count..)/sum(..count..), x=educ, fill="green"), alpha =.5) + geom_histogram(data = data %>% filter(race=="White"), aes(y=(..count..)/sum(..count..), x=educ, fill="red"), alpha =.5) 时如何防止轴改变？