## # RClimate Script:         RSS_lo_temp_anomaly.R                                #########
## Script stored on http://chartsgraphs.wordpress.com account for Users to source()       ##                                                                                       ## 
## Download and process  RSS MSU Satellite Data = TLT Temp Anomaly Trend Land & Ocean     ##
## Developed by D Kelly O'Day to demonstrate use of source() function for climate data    ##
##                   http:chartsgraphs.wordpress.com    2/5/10                            ##
############################################################################################

## Get Monthly anomaly data
 link<- "http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt"
  mo_RSS_in <- read.table(link, skip = 3, sep = "", header = F, as.is = T,
             colClasses = c(rep("numeric",3), rep("NULL", 8)),
             comment.char = "#", na.strings = c("*", "-",-99.9, -999.9),
             col.names = c("yr", "mo", "RSS_lo", rep("",8)))
  yr_frac <- mo_RSS_in$yr + (mo_RSS_in$mo-1)/12     # yr_frac simplifies calcs

## Create new data frame   
  RSS_df <- data.frame(yr_frac, mo_RSS_in)
  
## Get last mo, yr and anomaly to highlight last reading
  c <- nrow(RSS_df)                        # Find number of data rows
    lmo <- RSS_df$mo[c]                    # Fimd last month of data
    lyr <- RSS_df$yr[c]
    lyr_frac <- RSS_df$yr_frac[c]          # Find last year frac of data
    lRSS <- RSS_df$RSS_lo[c]                    # Find last reading

## Calc annual avg; vector must be sorted by date and include full monthly data for each year
   RSS_ann <- subset(RSS_df, RSS_df$yr >= 1979 & RSS_df$yr <2010)  $ set df to fulll years
   annavg= function(x) apply (array(x,dim=c(12,length(x)/12)),2,mean) 
   a_RSS <- annavg(RSS_ann$RSS_lo)
   n <- length(a_RSS)                   # number items sin vector
   a_RSS[n+1] <- a_RSS[n]               # add last yr so that step function will show across last yr
   a_RSS <- ts(a_RSS, start=1979, freq=1)

## Create RSS plot function
 pl_func <- function(){ 
     par(mfrow=c(1,1));par(oma=c(3,1,4,1)); par(mar=c(2,4,0,0)); par(ps=10)
     par(las=1); par(ps = c(9)) ; par(bty="l")

     plot(yr_frac, RSS_lo,  type="l",  col ="grey",  xlab = "",
       ylab = expression(paste("RSS Temperature Anomaly - ",degree,"C")),
       xlim=c(1979, 2012), ylim=c(-0.6, 0.80), xaxs="i", yaxs="i", axes = TRUE,
       cex.axis = 0.95, cex.lab = 0.95)
     abline(h=0, col = "grey")
     points(a_RSS, type = "s", col = "blue")  # show annual avg as blue step

  # Plot annotation
    n_text <- 0.9                 # use to control note font size
  # Establish plot titles
    title_3 <- expression(paste("RSS Land & Ocean Temperature Anomalies - ",degree, "C", sep=""))
    title_2 <- paste("Period: 1/1979  to ",lmo,"/",lyr, sep="")
    mtext(title_3, side = 3, line = 3, adj = 0.5)
    mtext(title_2, side = 3, line = 2, adj = 0.5, cex = n_text)
    mtext( "RSS Version 3.2 - MSU/AMSU TLT", side = 3,line = 1, adj=.5, cex = n_text)
  # Establish plot notes
     text(1980, 0.7, " Area: 70S to 82.5N", col = "black", pos =4, cex = n_text)
  # Highlight last reading
     points(lyr_frac, lRSS, col="red",pch=16)
     note <- paste(lmo, "/", lyr, " @ ", lRSS," C", sep="")
  # add legend
     legend(2000,-0.2, c("Annual Mean Anomaly",  "Monthly Anomaly" ,note), col = c("blue", "grey", "red"),
       text.col = "black", lty = c(1,1,0),pch=c(0,0,16),pt.cex=c(0,0,1),
       merge = F, bg = "white", bty="o", cex = .75, box.col="white")
  # Add margin notes for name and plot date
   #  mtext(link, side = 1, line = 2, adj=0.5, cex=0.8)       # link too long to fit on plot
      mtext("D Kelly O'Day, http://ChartsGraphs.Wordpress.Com", side = 1, line = 3, adj = 0, cex = 0.9)
      mtext(format(Sys.time(), "%m/%d/ %Y"), side = 1, line = 3, adj = 1, cex = 0.9)
   }

   pl_func()