This uses the hist
plot function in base R to give a histogram of size (long axis length) frequency within a taxa.
!!WARNING: this function uses hard coded plot attributes
vpr_plot_sizefreq(x, number_of_classes, colour_of_bar)
a data frame with columns 'taxa', 'long_axis_length'
numeric value passed to nclass argument in hist()
character value defining colour of plotted bars
K. Sorochan