# Plots the difference between two years from a contour plot created by plotContours These plots are normally used for plotting changes in the estimated concentration surface (whatSurface=3) but can be used to explore the changes in estimated surfaces for the log of concentration or for the standard error (in log space) which is what determines the bias correction. The difference can be shown either as an arithmetic difference or as a percentage difference. Although there are a lot of optional arguments to this function, most are set to a logical default. Data come from named list, which contains a Sample dataframe with the sample data, a Daily dataframe with the daily flow data, and an INFO dataframe with metadata. ```r plotDiffContours(eList, year0, year1, qBottom = NA, qTop = NA, maxDiff = NA, whatSurface = 3, tcl = 0.03, qUnit = 2, span = 60, pval = 0.05, printTitle = TRUE, plotPercent = FALSE, vert1 = NA, vert2 = NA, horiz = NA, flowDuration = TRUE, yTicks = NA, tick.lwd = 1, lwd = 2, cex.main = 0.95, cex.axis = 1, customPar = FALSE, usgsStyle = FALSE, color.palette = grDevices::colorRampPalette(c("blue", "white", "red")), concLab = 1, monthLab = 1, ...) ``` ## Arguments - `eList`: named list with at least the Daily and INFO dataframes, and surfaces matrix - `year0`: numeric value for the calendar year that is the first year of the pair of years for the analysis, should be a whole number - `year1`: numeric value for the calendar year that is the second year of the pair of years for the analysis, should be a whole number - `qBottom`: numeric value for the bottom edge of the graph, expressed in the units of discharge that are being used (as specified in qUnit). NA will choose a "pretty" lower limit nearest to the 5% of discharge. If yTicks are specified, then the first value of yTicks becomes the lowest discharge shown on the figure. - `qTop`: numeric value for the top edge of the graph, expressed in the units of discharge that are being used (as specified in qUnit). NA will choose a "pretty" upper limit nearest to the 95% of discharge. If yTicks are specified, then the last value of yTicks becomes the highest discharge shown on the figure. - `maxDiff`: numeric value which is the absolute value of the largest change in concentration that will be shown on the figure. If NA, the scale will be set from 5% to 95% of the concentration difference. If plotPercent = TRUE then maxDiff will be the maximum percentage difference. - `whatSurface`: numeric value, can only accept 1, 2, or 3; whatSurface = 1 is yHat (log concentration), whatSurface = 2 is SE (standard error of log concentration), and whatSurface = 3 is ConcHat (unbiased estimate of concentration), default = 3 - `tcl`: numeric, length of tick marks in inches, default is 0.1 - `qUnit`: object of qUnit class. `printqUnitCheatSheet`, or numeric represented the short code, or character representing the descriptive name. - `span`: numeric, it is the half-width (in days) of the smoothing window for computing the flow duration information, default = 60 - `pval`: numeric, the probability value for the lower flow frequency line on the graph - `printTitle`: logical variable if TRUE title is printed, if FALSE not printed - `plotPercent`: logical. If TRUE, plots percent difference, if FALSE, plots arithmetic differences. Defaults to FALSE. - `vert1`: numeric, the location in time for a black vertical line on the figure, yearStart < vert1 < yearEnd, default is NA (vertical line is not drawn) - `vert2`: numeric, the location in time for a black vertical line on the figure, yearStart < vert2 < yearEnd, default is NA (vertical line is not drawn) - `horiz`: numeric, the location in discharge for a black horizontal line on the figure, qBottom

plotDiffContours function