Dear list,
For educational purposes I have been working with the script below.
I have a observation:
line 31
#CScal[i] = (amo^2) # IT IS WRONG, I KNOW, BUT IT MAKE R TO CRASHES!
I'm thinking this is a possible bug in the R!
And I have a couple of doubts:
1) line 51
#curve(dchisq(x, n-1), add = T, col = 'red'
I think that it is correct, but the function no match with the observed
distribution.
curve(dchisq(x, n), add = T, col = 'red') matches, so, what is
wrong?
2) Plot
I would like to distance the Ylabel from the left limit of the screen, is it
possible?
Many thanks,
--
Jos?? Cl??udio Faria
Brasil/Bahia/UESC/DCET
Estat??stica Experimental/Prof. Adjunto
mails:
joseclaudio.faria at terra.com.br
jc_faria at uesc.br
jc_faria at uol.com.br
# Title : Origin chi-square distribution
# Author : Jos?? Cl??udio Faria
# Date : 16/12/2004
# Version : v1
#-------------------------------------------------------------------------------
#---------------------- Begin informations
-----------------------------------
# Populational parameters
Mpop = 0 # Mean
Vpop = 1 # Variance
N = 10000 # Size
# Sampling
n = 10 # size of the sample
sr = 10000 # sampling repetition
# Plot parameter
nchist = 150
#---------------------- End informations
-------------------------------------
CScal = numeric(); # CScal = Chi-square calculated
pop = rnorm(N, Mpop, sqrt(Vpop)) # pop~N(Mpop,Vpop)
for (i in 1:sr)
{
amo = sample(pop, n, replace = TRUE)
#===================================================================
#CScal[i] = (amo^2) # IT IS WRONG, I KNOW, BUT IT MAKE R TO CRASHES!
#===================================================================
CScal[i] = sum(amo^2)
}
win.graph(w = 6, h = 7)
split.screen(c(2,1))
screen(1)
hist(CScal, breaks = nchist, col = 'gray', main =
'Histogram',
xlab = NULL, ylab = 'Absolute frequence', font.lab = 2, font =
2)
mtext(expression(chi^2==sum(amo^2)), side = 3, col = 'red', font = 2)
screen(2)
hist(CScal, probability = T, breaks = nchist, col = 'gray', main =
'Density',
xlab = expression(chi^2), ylab = expression(f(chi^2)), font.lab = 2,
font = 2)
mtext(expression(chi^2==sum(amo^2)), side = 3, col = "red", font =
2)
x = CScal
#========================================== # I THINK THIS WAY IS CORRECT
(n-1)
#curve(dchisq(x, n-1), add = T, col = 'red')
#========================================== curve(dchisq(x, n), add = T,
col = 'red')
cat('\nPopulation:'); cat('\n')
cat('\tMean =', Mpop); cat('\n')
cat('\tVariance =', Vpop); cat('\n')
cat('\tSize (N) =', N); cat('\n')
cat('\nSample:'); cat('\n')
cat('\tSize (n) =', n, '->', (n - 1), 'df');
cat('\n')
cat('\nSampling:'); cat('\n')
cat('\tRepetitions =', sr); cat('\n\n')