R/PlotHydrophobicity.R

In BioAlvaro/MQviewer: Quality Control of Protemics Data

#' Peptide hydrophobicity by GRAVY score
#'
#' @param MQCombined Object list containing all the files from the MaxQuant
#' output. It is the result from using \code{make_MQCombined}.
#' @param show_median If true it will show the median of each group, as a red
#'  dashed line.By default is TRUE.
#' @param binwidth Selects the binwidth of the histogram. By default = 0.2
#' @param palette The palette from the Package RColorBrewer. By default is
#' 'Set2'.
#' @param size_median The width of the median line in the plots.
#' @param plots_per_page Establish the maximum number of plots per page.
#' @param tabular_output If true a table with the information will be the
#' output.
#'
#' @return Returns a histogram per sample, showing the frequency of the
#'  peptide's hydrophobicity GRAVY value.
#'
#' @export
#'
#' @examples
#' MQPathCombined <- system.file("extdata/combined/", package = "MQmetrics")
#' MQCombined <- make_MQCombined(MQPathCombined)
#' PlotHydrophobicity(MQCombined)
PlotHydrophobicity <- function(MQCombined,
                            show_median = TRUE,
                            size_median = 1.5,
                            binwidth = 0.2,
                            palette = "Set2",
                            plots_per_page = 5,
                            tabular_output = FALSE) {
    peptides <- MQCombined$peptides.txt

    variable <- GRAVY <- `median(GRAVY)` <- NULL

    df <- peptides %>% select(contains(c("Length",
                                        "Count",
                                        "Sequence",
                                        "Experiment")
    )
    )

    df$GRAVY <- (df$`A Count` * 1.8 +
                df$`R Count` * -4.5 +
                df$`N Count` * -3.5 +
                df$`D Count` * -3.5 +
                df$`C Count` * 2.5 +
                df$`Q Count` * -3.5 +
                df$`E Count` * -3.5 +
                df$`G Count` * -0.4 +
                df$`H Count` * -3.2 +
                df$`I Count` * 4.5 +
                df$`L Count` * 3.8 +
                df$`K Count` * -3.9 +
                df$`M Count` * 1.9 +
                df$`F Count` * 2.8 +
                df$`P Count` * -1.6 +
                df$`S Count` * -0.8 +
                df$`T Count` * -0.7 +
                df$`W Count` * -0.9 +
                df$`Y Count` * -1.3 +
                df$`V Count` * 4.2) / df$Length


    df <- df %>% select(contains(c("GRAVY", "Experiment")))

    df_out <- melt(df, id.vars = "GRAVY")

    df_out$variable <- gsub("Experiment ", "", df_out$variable)

    # Remove value 0,

    df_out <- df_out[!is.na(df_out$value), ]


    # Repeat rows n numbers of times, being n the frequency (value)
    df_expanded <- df_out[rep(rownames(df_out), df_out$value), ]



    if (tabular_output == TRUE) {

        GRAVY <- df_expanded %>%
            group_by(variable) %>%
            summarise(Mean = format(round(mean(GRAVY),2),nsmall = 1),
                      Max = format(round(max(GRAVY),2),nsmall = 1),
                      Min = format(round(min(GRAVY),2),nsmall = 1),
                      Median = format(round(median(GRAVY),2),nsmall = 1))
        names(GRAVY)[1] <- 'Experiment'

        return(GRAVY)
    }

    colourCount <- length(df) - 1

    getPalette <- colorRampPalette(brewer.pal(8, palette))

    n_pages_needed <- ceiling(
        (colourCount) / plots_per_page
    )

    myplots <- list()

    for (ii in seq_len(n_pages_needed)) {
        if ((length(df) - 1) < plots_per_page) {
            nrow <- length(df) - 1
        } else {
            nrow <- plots_per_page
        }

        p <- df_expanded %>%
                group_by(variable) %>%
                ggplot(aes(x = GRAVY, fill = variable, group = variable)) +
                geom_histogram(color = "black", binwidth = binwidth) +
                facet_wrap_paginate(. ~ variable,
                                    ncol = 1,
                                    nrow = nrow,
                                    page = ii) +
                theme_bw() +
                theme(legend.position = "none") +
                scale_fill_manual(values = getPalette(colourCount)) +
                ggtitle("Peptide hydropathy distribution") +
                ylab("Peptide Frequency") +
                xlab("GRAVY score")

        if (show_median == TRUE) {
            median_groups <- df_expanded %>%
                group_by(variable) %>%
                summarise(median(GRAVY))

            p <- p + geom_vline(
                data = median_groups,
                aes(xintercept = `median(GRAVY)`, group = variable),
                color = "red",
                linetype = "dashed",
                size = size_median
                )
        }
        myplots[[ii]] <- p
    }
    return(myplots)
}