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WeiQiang.Li@seagate.com

2004-Mar-01 09:18 UTC

[R] How to plot Histogram with frequence overlaid by distribution curve

Hi,
      I am facing the problem that I want to plot a histogram chart set
freq to true and overlay with normal or weibull or exponential distribution
curve.

      The sample code is shown as below:
     
>samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,
      -8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
      -8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
      -7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
      -7.28924,-6.78729,-6.25307)

      >hist(samp,freq=TRUE,br=20)
      >curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)

      In the chart created based on above command, curve scale is too small
compared to the freqeunce. My question here is how to adjust the scale of
distribution curve. Thanks !

Best Regards
WeiQiang Li

Gabor Grothendieck

2004-Mar-01 12:12 UTC

head link

[R] How to plot Histogram with frequence overlaid by distribution curve

histdata <- hist(samp,freq=TRUE,br=20)
curve(max(histdata$count)*dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)

---
Date:   Mon, 1 Mar 2004 17:18:12 +0800 
From:   <WeiQiang.Li at seagate.com>
To:   <r-help at stat.math.ethz.ch> 
Subject:   [R] How to plot Histogram with frequence overlaid by distribution
curve

 
Hi,
I am facing the problem that I want to plot a histogram chart set
freq to true and overlay with normal or weibull or exponential distribution
curve.

The sample code is shown as below:>samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,-8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
-8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
-7.28924,-6.78729,-6.25307)
>hist(samp,freq=TRUE,br=20)
>curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
In the chart created based on above command, curve scale is too small
compared to the freqeunce. My question here is how to adjust the scale of
distribution curve. Thanks !

Best Regards
WeiQiang Li

Rolf Turner

2004-Mar-01 13:43 UTC

head link

[R] How to plot Histogram with frequence overlaid by distribution curve

In response to a posting from WeiQiang Li:
> Hi,
> I am facing the problem that I want to plot a histogram chart set
> freq to true and overlay with normal or weibull or exponential distribution
> curve.
> 
> The sample code is shown as below:
> >samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,
> -8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
> -8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
> -7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
> -7.28924,-6.78729,-6.25307)
> 
> >hist(samp,freq=TRUE,br=20)
> >curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
> 
> In the chart created based on above command, curve scale is too small
> compared to the freqeunce. My question here is how to adjust the scale of
> distribution curve. Thanks !
> 
Gabor Grothendieck wrote:
> histdata <- hist(samp,freq=TRUE,br=20)
> curve(max(histdata$count)*dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
This is a perfectly correct answer to a question that should not have
been asked in the first place.  What WeiQiang Li proposes to do makes
no sense at all, and will simply confuse and mislead the viewer/reader.
If a histogram is to be overlaid with a density curve that histogram
should represent a density and hence should be plotted on the density
scale --- NOT on the frequency scale.

				cheers,

					Rolf Turner
					rolf at math.unb.ca

Spencer Graves

2004-Mar-01 15:18 UTC

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[R] How to plot Histogram with frequence overlaid by distribution curve

?truehist in library(MASS)? 

library(MASS)
truehist(samp)
x <- seq(-8.5, -6, length=51)
lines(x, dnorm(x, mean(samp), sqrt(var(samp))))

      This just worked for me in both S-Plus 6.2 and R 1.8.1.
hope this helps.  spencer graves
Rolf Turner wrote:
>In response to a posting from WeiQiang Li:
>
>  
>
>>Hi,
>>I am facing the problem that I want to plot a histogram chart set
>>freq to true and overlay with normal or weibull or exponential
distribution
>>curve.
>>
>>The sample code is shown as below:
>>    
>>
>>>samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,
>>>      
>>>
>>-8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
>>-8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
>>-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
>>-7.28924,-6.78729,-6.25307)
>>
>>    
>>
>>>hist(samp,freq=TRUE,br=20)
>>>curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
>>>      
>>>
>>In the chart created based on above command, curve scale is too small
>>compared to the freqeunce. My question here is how to adjust the scale
of
>>distribution curve. Thanks !
>>
>>    
>>
>
>Gabor Grothendieck wrote:
>
>  
>
>>histdata <- hist(samp,freq=TRUE,br=20)
>>curve(max(histdata$count)*dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
>>    
>>
>
>This is a perfectly correct answer to a question that should not have
>been asked in the first place.  What WeiQiang Li proposes to do makes
>no sense at all, and will simply confuse and mislead the viewer/reader.
>If a histogram is to be overlaid with a density curve that histogram
>should represent a density and hence should be plotted on the density
>scale --- NOT on the frequency scale.
>
>				cheers,
>
>					Rolf Turner
>					rolf at math.unb.ca
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>  
>

Rolf Turner

2004-Mar-01 20:48 UTC

head link

[R] How to plot Histogram with frequence overlaid by distribution curve

Spencer Graves wrote:
> ?truehist in library(MASS)? 
> 
> library(MASS)
> truehist(samp)
> x <- seq(-8.5, -6, length=51)
> lines(x, dnorm(x, mean(samp), sqrt(var(samp))))
> This just worked for me in both S-Plus 6.2 and R 1.8.1.
	What's wrong with ``hist(samp,prob=TRUE)''?
> hope this helps.  spencer graves
	I wasn't aware that I was in need of any help.  I merely made
	a comment on a wrong-headed question that was addressed to
	this list.


				cheers,

					Rolf Turner

WeiQiang.Li@seagate.com

2004-Mar-04 06:26 UTC

head link

[R] How to plot Histogram with frequence overlaid by distribution curve

Hi,

      I am having a new problem that how I can set the probability scale
from 0 to 1 when I using on probability scale. Sometimes I get the maximum
probabilty more than 100%.

      Thanks!

Best Regards,
WeiQiang

In response to a posting from WeiQiang Li:
> Hi,
> I am facing the problem that I want to plot a histogram chart set
> freq to true and overlay with normal or weibull or exponential
distribution> curve.
>
> The sample code is shown as below:
> >samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,
> -8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
> -8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
> -7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
> -7.28924,-6.78729,-6.25307)
>
> >hist(samp,freq=TRUE,br=20)
> >curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
>
> In the chart created based on above command, curve scale is too small
> compared to the freqeunce. My question here is how to adjust the scale of
> distribution curve. Thanks !
>
Gabor Grothendieck wrote:
> histdata <- hist(samp,freq=TRUE,br=20)
> curve(max(histdata$count)*dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
This is a perfectly correct answer to a question that should not have
been asked in the first place.  What WeiQiang Li proposes to do makes
no sense at all, and will simply confuse and mislead the viewer/reader.
If a histogram is to be overlaid with a density curve that histogram
should represent a density and hence should be plotted on the density
scale --- NOT on the frequency scale.

                                                 cheers,

                                                             Rolf Turner

rolf at math.unb.ca

Rolf Turner

2004-Mar-04 11:55 UTC

head link

[R] How to plot Histogram with frequence overlaid by distribution curve

You wrote:
> I am having a new problem that how I can set the probability scale
> from 0 to 1 when I using on probability scale. Sometimes I get the
> maximum probabilty more than 100%.
When you set prob=TRUE you get a ***density*** scale.  The resulting
histogram represents a probability density function (directly comparable
with the normal density function you sought to superimpose) which
***integrates*** to 1.  The values of a density funcion need not
be less than 1; these values are not probabilities.  They are probability
densities.  Roughly if f(x) is the p.d.f. for X then

		f(x) dx approx. = P(x <= X <= x + dx)

I.e. f(x) dx will be less than 1, but f(x) on its own need not be.

O.K.?

					cheers,

						Rolf Turner
						rolf at math.unb.ca

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