[R] chisq.test using amalgamation automatically (possible ?!?)

[Mohammad Ehsanul Karim]

Dear List,


If any of observed and/or expected data has less than
5 frequencies, then  chisq.test (Pearson's Chi-squared
Test for Count Data from package:stats) gives warning
messages. For example,

x<-c(10, 14, 10, 11, 11, 7, 8, 4, 1, 4, 4, 2, 1, 1, 2,
1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1)
y<-c(9.13112391745095, 13.1626482033341,
12.6623267638188, 11.0130706413029, 9.16415925139016,
7.47441794889028, 6.03743388141852, 4.85350508692505,
3.89248001363859, 3.11803140037476, 2.49617540962629,
1.99774139023269, 1.5985926374167, 1.27909653584089,
1.02341602646530, 0.818828097315106,
0.655132353196336, 0.524159229418155,
0.418022824890164, 0.335528136508225,
0.268448671671046, 0.214779801990545,
0.171840507806838, 0.137485729582785,
0.109999238967747, 0.0880079144684513,
0.070413150156564)

Chi.Sq<-sum((c(x[1:7], sum(x[8:9]), sum(x[10:11]),
sum(x[12:27]))-c(y[1:7], sum(y[8:9]), sum(y[10:11]),
sum(y[12:27])))^2/c(y[1:7], sum(y[8:9]),
sum(y[10:11]), sum(y[12:27]))) # using amalgamation
pchisq(Chi.Sq, df=9, ncp=0, lower.tail = FALSE, log.p
= FALSE) # result being 0.8830207

but chisq.test(x,y) gives the following output with
incorrect df:

        Pearson's Chi-squared test

data:  x and y 
X-squared = 216, df = 208, p-value = 0.3373

Warning message:
Chi-squared approximation may be incorrect in:
chisq.test(x, y) 



Is there any way that we can use directly chisq.test
without having warning message in such cases (that is,
using amalgamation conveniently so that we don't have
to check each elements if they are less than 5 or not
- the whole process being automatic, may be by means
of programming)?



Any hint, help, support, references will be highly
appreciated.
Thank you for your time. 

----------------------------------

Mohammad Ehsanul Karim 

Web: http://snipurl.com/ehsan 
ISRT, University of Dhaka, BD 

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