如何使for循环工作以自动绘图

Question

我有

• 一个data.frame df

  df = data.frame(year=c(2018,2019,2020), value1=rnorm(3,1,0.5), value2=rnorm(3,2,0.5)

• 一个名为 ScatterPlot 的 ggplot 函数（函数代码见下文）

• 一个for loop，我想用它在我的df上运行ggplot函数

我的意图是自动（使用 scatterplot 函数和我的 for 循环）绘制（散点）多年来的 value1 和多年的 value2。

由于某种原因，下面的 for 循环仅生成一个图（我的 df 中的最后一个）。谁能告诉我我错过了什么？

for循环：

# Create the loop.vector (all the columns)
loop.vector <- ncol(df)-1

for (i in loop.vector) { # Loop over loop.vector
        
        # store data in column.i as x
        x <- df[i]

        x = unlist(x) #necessary. otherwise ggplot will generate an error
        
        plotname = colnames(df[i])
        
        #plot
        
        jpeg(filename=paste0("/R-Outputs/plots/",plotname,".jpeg"))
        
        plot= ScatterPlot(df,df$year,"year", x, plotname)
       
        print(plot)
        
        dev.off()
}

散点图函数（可行）：

ScatterPlot <- function(df, x, x_var_label,y, y_var_label) {
# Input: 
#     df: a data frame
#     x: a column from df in the form of a character vector
#     y: a column from df in the form of a character vector
#
# Output:
#     a ggplot2 plot

require(ggplot2)
        
x_title = x_var_label
y_title = y_var_label
        
time_labels = c("2018", "2019", "2020")
        
ggplot(data = df, aes(x = x, y = y)) +
        geom_point(col="#69b3a2",fill="#69b3a2",alpha=0.5, size = 0) +
        geom_line()+
        geom_smooth(method = "lm", se = FALSE, size = 0.8, col="red") +
        xlab(label = x_title) +
        ylab(label = y_title) +
        theme_bw()+
        theme(axis.text.x=element_text(angle=45, hjust = 1))+
        labs(title = paste0(y_title," over time"))+
        scale_x_continuous("year", labels = as.character(time_labels), 
        breaks = as.integer((time_labels)))
        
}

Answer 1

您不需要同时传递值和列名。只传递函数ScatterPlot中的列名。

library(ggplot2)

ScatterPlot <- function(df, x_var_label,y_var_label) {
  # Input: 
  #     df: a data frame
  #     x: a column from df in the form of a character vector
  #     y: a column from df in the form of a character vector
  #
  # Output:
  #     a ggplot2 plot
  
  time_labels = c("2018", "2019", "2020")
  
  ggplot(data = df, aes(x = .data[[x_var_label]], y = .data[[y_var_label]])) +
    geom_point(col="#69b3a2",fill="#69b3a2",alpha=0.5, size = 0) +
    geom_line()+
    geom_smooth(method = "lm", se = FALSE, size = 0.8, col="red") +
    xlab(label = x_var_label) +
    ylab(label = y_var_label) +
    theme_bw()+
    theme(axis.text.x=element_text(angle=45, hjust = 1))+
    labs(title = paste0(y_var_label," over time"))+
    scale_x_continuous("year", labels = time_labels, 
                       breaks = as.integer(time_labels))
  
}

要在循环中调用这个函数，这样的事情应该可以工作。

#column names to loop over
loop.vector <- names(df[-1])
plot <- vector('list', length(loop.vector))

for (i in seq_along(loop.vector)) { # Loop over loop.vector
  jpeg(filename=paste0("/R-Outputs/plots/",loop.vector[i],".jpeg"))
  plot[[i]] = ScatterPlot(df,"year", loop.vector[i])
  print(plot[[i]])
  dev.off()
}

我们还将单个地块保存在一个列表中，您可以使用plot[[1]]、plot[[2]] 等进行验证。