-------- Graphing functions -------- 

 
histo       : Plot a histogram
k_pdf       : Plots a univariate kernel density
pairs       : Pairwise scatter plots of the columns of x
pairs_d     : demo of pairs (pairwise scatterplots)
plt_turns   : plot turning points in a time series
plt_turnsd  : demo of fturns() 
pltdens     : Draw a nonparametric density estimate. 
pltdens_d   : demo of pltdens (non-parameter density plot)
spyc        : colorful version of matlab spy.c function
tsplot      : time-series plot with dates and labels
tsplot_d    : demo of tsplot (time-series plot)