[R] Changing x-axis when dealing with time

From: Pablo Rosado <pablojrosado_at_lbl.gov>
Date: Fri, 13 May 2011 18:15:57 -0700


Hi,

I am plotting data in which the x values are a timestamp. I am trying to change the x-ticks so they will be in specified hours of the day, but it always start from hour 4 of the day. And I need it to start from the beginning of the axis (at x=0) and then each tick be on the interval I specify.

Here is my plotting script:

*##-- ROOF COMPARISON - SOUTH--
win.graph()
plot(x=tiempo,y=timeframe[,8],xlab="",ylab="",**xaxt='n',** yaxt='n',type="l",col="blue",lwd=3,ylim=c(0,80),font=2,las=1) axis(side=1,at=seq(0,24,3))
axis(side=2,at=seq(0,80,10),line=NA, tcl = -0.5,font=2,las=1)

lines(x=tiempo,y=timeframe[,47],col="red",lwd=3)
title(xlab=paste("Local Standard Time (",date), cex.lab=1,font.lab=2)
title(ylab="Temperature (C)", cex.lab=1,font.lab=2)
legend("topleft",legend=c("cool", "standard"),col=c("blue", "red"),lwd=c(4,4),bty="n",cex=1.25)
grid(nx=NULL,ny=NULL,col = "gray", lty = "dotted",lwd = 1)*

But with the axis(side=1...) nothing appears.

I have been practicing with the following code to change the xaxis but it says that x and y lengths differ:

*## TIMESTAMP IS A ONE COLUMN VECTOR IN WHICH I SAVED THE TIMESTAMP FROM MY FILE
string.to.time <-

    function(timestamp)

        strptime(x=timestamp, format="%Y-%m-%d %H:%M:%S")

decimal.day <-

    function(timestamp) {

        y <- as.POSIXlt(**timestamp**)
        y$day + y$hour/24 + y$min/(24*60) + y$sec/(24*60*60)

}

decimal.hour <-

    function(**timestamp**) {

        dd <- decimal.day(**timestamp**)
        24 * (dd - floor(dd))

}

 ##create some data to plot

t.start <- string.to.time("2011-05-02 00:00:00")
t.start
t.vector <- t.start + (0:24)*3600
t.vector
z.vector <- 1:length(t.vector)
z.vector

##vector of decimal hours
dh.vector <- decimal.hour(t.vector)
dh.vector

plot(x=dh.vector, y=z.vector, xlim=c(0,24), xaxt="n", xlab="Hour of day", ylab="Some property")
 *

Thank You so much and have a great weekend.

-- 
*Pablo J. Rosado*, *Ph.D. Student*
*Graduate Student Researcher Assistant*
*University of California - Berkeley*
*Lawrence Berkeley National* *Lab** *||* *EET Division* *|| *Heat Island
Group
Office (510) 495-2329
Cell: (787) 399-7635
*

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Received on Sat 14 May 2011 - 01:20:11 GMT

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