[R] Probabilities greather than 1 in HIST
Dear all,
I am a newbie in R and could not find help on this problem. I am trying to
plot an histogram with probabilities in the y axis. This is the code I am
using:
#TLC uniform
n=30
mi=1; mx=6
nrep=1000
xbar=rep(0,nrep)
for (i in 1:nrep) {xbar[i]=mean(runif(n,min=mi,max=mx))}
hist(xbar,prob=TRUE,breaks="Sturges",xlim=c(1,6),main=paste("n =",n),
xlab="Média", ylab="Probabilidade")
curve(dnorm(x,mean=mean(xbar),sd=sd(xbar)),add=TRUE,lwd=2,col="red")
The problem is that I am getting greater than 1 probabilities in the Y axis?
Is there a way to correct this?
Many thanks in advance.
Joao
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Re: [R] Probabilities greather than 1 in HIST
Dear David,
Thanks for your prompt reply.
I see your point. But how can I get a histogram with relative frequencies? If I
use
>plot(xhist,yhist)
I get absolute frequencies in the Y axis.
Best,
Joao
From: David Winsemius [via R]
[mailto:ml-node+619-1272092771-215...@n4.nabble.com]
Sent: quinta-feira, 3 de Março de 2011 16:01
To: jpmaroco
Subject: Re: Probabilities greather than 1 in HIST
On Mar 3, 2011, at 8:03 AM, jpmaroco wrote:
> Dear all,
> I am a newbie in R and could not find help on this problem. I am
> trying to
> plot an histogram with probabilities in the y axis. This is the code
> I am
> using:
>
> #TLC uniform
> n=30
> mi=1; mx=6
> nrep=1000
> xbar=rep(0,nrep)
> for (i in 1:nrep) {xbar[i]=mean(runif(n,min=mi,max=mx))}
> hist(xbar,prob=TRUE,breaks="Sturges",xlim=c(1,6),main=paste("n =",n),
> xlab="Média", ylab="Probabilidade")
> curve(dnorm(x,mean=mean(xbar),sd=sd(xbar)),add=TRUE,lwd=2,col="red")
>
> The problem is that I am getting greater than 1 probabilities in the
> Y axis?
> Is there a way to correct this?
Despite the argument name, which I agree suggests that probabilities
will be plotted, what is really described in the help page is that
densities will be plotted, and densities may be greater than 1. You
can suppress plotting of the y-axis, calculate the probabilities for
each of the groups returned by hist, and then use the axes function.
> xhist <- hist(xbar,breaks="Sturges",plot=FALSE)
> yhist <- xhist$counts/sum(xhist$counts)
> yhist
[1] 0.002 0.027 0.087 0.236 0.287 0.228 0.107 0.021 0.004 0.001
> Many thanks in advance.
> Joao
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html
>
> <http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html?by-user=t>
>
> Sent from the R help mailing list archive at Nabble.com.
> [[alternative HTML version deleted]]
>
> __
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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Re: [R] Probabilities greather than 1 in HIST
Hi Martin,
No, I get frequencies greather than 1.
See the code:
#TLC uniform
n=30
mi=1; mx=6
nrep=1000
xbar=rep(0,nrep)
for (i in 1:nrep) {xbar[i]=mean(runif(n,min=mi,max=mx))}
hist(xbar, freq=FALSE)
#hist(xbar,prob=TRUE,breaks="Sturges",xlim=c(1,6),main=paste("n =",n),
xlab="Média", ylab="Probabilidade")
curve(dnorm(x,mean=mean(xbar),sd=sd(xbar)),add=TRUE,lwd=2,col="red")
Thanks anyway
Best
Jº
From: Martyn Byng [via R]
[mailto:ml-node+757-242386738-215...@n4.nabble.com]
Sent: quinta-feira, 3 de Março de 2011 17:12
To: jpmaroco
Subject: Re: Probabilities greather than 1 in HIST
Hi,
Does
xx = rnorm(100)
hist(xx,freq=FALSE)
curve(dnorm,add=TRUE)
give you what you want?
Martyn
-Original Message-
From: [hidden email] [mailto:[hidden email]] On Behalf Of David Winsemius
Sent: 03 March 2011 17:00
To: jpmaroco
Cc: [hidden email]
Subject: Re: [R] Probabilities greather than 1 in HIST
On Mar 3, 2011, at 10:29 AM, jpmaroco wrote:
> Dear David,
>
> Thanks for your prompt reply.
>
> I see your point. But how can I get a histogram with relative
> frequencies? If I use
>
>> plot(xhist,yhist)
>
> I get absolute frequencies in the Y axis.
In my earlier reply I meant to type yaxt="n".
--
David.
>
> Best,
>
> Joao
>
>
>
> From: David Winsemius [via R] [mailto:[hidden email]
> ]
> Sent: quinta-feira, 3 de Março de 2011 16:01
> To: jpmaroco
> Subject: Re: Probabilities greather than 1 in HIST
>
>
>
>
> On Mar 3, 2011, at 8:03 AM, jpmaroco wrote:
>
>
>> Dear all,
>> I am a newbie in R and could not find help on this problem. I am
>> trying to
>> plot an histogram with probabilities in the y axis. This is the code
>> I am
>> using:
>>
>> #TLC uniform
>> n=30
>> mi=1; mx=6
>> nrep=1000
>> xbar=rep(0,nrep)
>> for (i in 1:nrep) {xbar[i]=mean(runif(n,min=mi,max=mx))}
>> hist(xbar,prob=TRUE,breaks="Sturges",xlim=c(1,6),main=paste("n =",n),
>> xlab="Média", ylab="Probabilidade")
>> curve(dnorm(x,mean=mean(xbar),sd=sd(xbar)),add=TRUE,lwd=2,col="red")
>>
>> The problem is that I am getting greater than 1 probabilities in the
>> Y axis?
>> Is there a way to correct this?
>
>
> Despite the argument name, which I agree suggests that probabilities
> will be plotted, what is really described in the help page is that
> densities will be plotted, and densities may be greater than 1. You
> can suppress plotting of the y-axis, calculate the probabilities for
> each of the groups returned by hist, and then use the axes function.
>
>> xhist <- hist(xbar,breaks="Sturges",plot=FALSE)
>> yhist <- xhist$counts/sum(xhist$counts)
>> yhist
> [1] 0.002 0.027 0.087 0.236 0.287 0.228 0.107 0.021 0.004 0.001
>
>
>
>
>> Many thanks in advance.
>> Joao
>>
>> --
>> View this message in context:
>> http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html
>>
>> <http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html?by-user=t>
>>
>>
>> <http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html?by-user=t
>>
>> <http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p388.html?by-user=t&by-user=t>
>>
>> >
>> Sent from the R help mailing list archive at Nabble.com.
>> [[alternative HTML version deleted]]
>>
>> __
>> [hidden email] mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
> __
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
>
> _
>
> If you reply to this email, your message will be added to the
> discussion below:
>
> http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p619.html
>
> <http://r.789695.n4.nabble.com/Probabilities-greather-than-1-in-HIST-tp388p619.html?by-user=t>
>
>
