R/plot_ma.R

In federicomarini/ideal: Interactive Differential Expression AnaLysis

#' MA-plot from base means and log fold changes
#'
#' MA-plot from base means and log fold changes, in the ggplot2 framework, with
#' additional support to annotate genes if provided.
#'
#' The genes of interest are to be provided as gene symbols if a \code{symbol}
#' column is provided in \code{res_obj}, or else by using  the identifiers specified
#' in the row names
#'
#' @param res_obj A \code{\link{DESeqResults}} object
#' @param FDR Numeric value, the significance level for thresholding adjusted p-values
#' @param point_alpha Alpha transparency value for the points (0 = transparent, 1 = opaque)
#' @param sig_color Color to use to mark differentially expressed genes. Defaults to red
#' @param annotation_obj A \code{data.frame} object, with row.names as gene
#' identifiers (e.g. ENSEMBL ids) and a column, \code{gene_name}, containing
#' e.g. HGNC-based gene symbols. Optional
#' @param draw_y0 Logical, whether to draw the horizontal line at y=0. Defaults to
#' TRUE.
#' @param hlines The y coordinate (in absolute value) where to draw horizontal lines,
#' optional
#' @param title A title for the plot, optional
#' @param xlab X axis label, defaults to "mean of normalized counts - log10 scale"
#' @param ylim Vector of two numeric values, Y axis limits to restrict the view
#' @param add_rug Logical, whether to add rug plots in the margins
#' @param intgenes Vector of genes of interest. Gene symbols if a \code{symbol}
#' column is provided in \code{res_obj}, or else the identifiers specified in the
#' row names
#' @param intgenes_color The color to use to mark the genes on the main plot.
#' @param labels_intgenes Logical, whether to add the gene identifiers/names close
#' to the marked plots
#' @param labels_repel Logical, whether to use \code{geom_text_repel} for placing the
#' labels on the features to mark
#'
#' @return An object created by \code{ggplot}
#' @export
#'
#' @examples
#' library(airway)
#' data(airway)
#' airway
#' dds_airway <- DESeq2::DESeqDataSetFromMatrix(assay(airway),
#'   colData = colData(airway),
#'   design = ~ cell + dex
#' )
#' # subsetting for quicker run, ignore the next two commands if regularly using the function
#' gene_subset <- c(
#'   "ENSG00000103196", # CRISPLD2
#'   "ENSG00000120129", # DUSP1
#'   "ENSG00000163884", # KLF15
#'   "ENSG00000179094", # PER1
#'   rownames(dds_airway)[rep(c(rep(FALSE, 99), TRUE), length.out = nrow(dds_airway))]
#' ) # 1% of ids
#' dds_airway <- dds_airway[gene_subset, ]
#'
#' dds_airway <- DESeq2::DESeq(dds_airway)
#' res_airway <- DESeq2::results(dds_airway)
#'
#' plot_ma(res_airway, FDR = 0.05, hlines = 1)
#'
#' plot_ma(res_airway,
#'   FDR = 0.1,
#'   intgenes = c(
#'     "ENSG00000103196", # CRISPLD2
#'     "ENSG00000120129", # DUSP1
#'     "ENSG00000163884", # KLF15
#'     "ENSG00000179094"  # PER1
#'   ) 
#' )
plot_ma <- function(res_obj,
                    FDR = 0.05,
                    point_alpha = 0.2,
                    sig_color = "red",
                    annotation_obj = NULL, # TODO: add a check, if not available skip this part
                    draw_y0 = TRUE,
                    hlines = NULL,
                    title = NULL,
                    xlab = "mean of normalized counts - log10 scale",
                    ylim = NULL,
                    add_rug = TRUE,
                    intgenes = NULL,
                    intgenes_color = "steelblue",
                    labels_intgenes = TRUE,
                    labels_repel = TRUE) {
  ma_df <- data.frame(
    mean = res_obj$baseMean,
    lfc = res_obj$log2FoldChange,
    padj = res_obj$padj,
    isDE = ifelse(is.na(res_obj$padj), FALSE, res_obj$padj < FDR),
    ID = rownames(res_obj)
  )

  ma_df <- ma_df[ma_df$mean > 0, ]

  if (!is.null(annotation_obj)) {
    ma_df$genename <- annotation_obj$gene_name[match(ma_df$ID, rownames(annotation_obj))]
  }

  ma_df$logmean <- log10(ma_df$mean) # TO ALLOW FOR BRUSHING!!
  # ma_df$DE <- ifelse(ma_df$isDE,"yes","no")
  ma_df$DE <- ifelse(ma_df$isDE, "red", "black")

  p <- ggplot(ma_df, aes_string(x = "logmean", y = "lfc", colour = "DE"))

  if (!is.null(hlines)) {
    p <- p + geom_hline(aes(yintercept = hlines), col = "lightblue", alpha = 0.4) +
      geom_hline(aes(yintercept = -hlines), col = "lightblue", alpha = 0.4)
  }
  
  if (draw_y0)
    p <- p + geom_hline(aes(yintercept = 0), col = "red", alpha = 0.4)

  p <- p + xlab(xlab) + ylab("log fold change")

  p <- p + geom_point(alpha = point_alpha)
  p <- p + scale_colour_manual(
    name = paste0("FDR = ", FDR),
    values = c("black", sig_color),
    labels = c("nonDE", "DE")
  )

  if (!is.null(ylim)) {
    p <- p + coord_cartesian(ylim = ylim)
  }

  if (!is.null(title)) {
    p <- p + ggtitle(title)
  }

  if (!is.null(intgenes)) {

    # now here for the symbol
    res_df <- as.data.frame(res_obj)
    res_df$logmean <- log10(res_df$baseMean)

    if ("symbol" %in% colnames(res_df)) {
      # use the gene names
      df_intgenes <- res_df[res_df$symbol %in% intgenes, ]
      df_intgenes$myids <- df_intgenes$symbol
    } else {
      # use whatever is there as id
      df_intgenes <- res_df[rownames(res_df) %in% intgenes, ]
      df_intgenes$myids <- rownames(df_intgenes)
    }

    # df_intgenes <- res_df[res_df$symbol %in% intgenes,]
    p <- p + geom_point(data = df_intgenes, aes_string("logmean", "log2FoldChange"), color = intgenes_color, size = 4)

    if (labels_intgenes) {
      if (labels_repel) {
        p <- p + geom_text_repel(
          data = df_intgenes, aes_string("logmean", "log2FoldChange", label = "myids"),
          color = intgenes_color, size = 5
        )
      } else {
        p <- p + geom_text(
          data = df_intgenes, aes_string("logmean", "log2FoldChange", label = "myids"),
          color = intgenes_color, size = 5, hjust = 0.25, vjust = -0.75
        )
      }
    }
  }

  if (add_rug) {
    p <- p + geom_rug(alpha = 0.3)
  }

  p <- p + theme_bw()
  p
}