Dear Lalitha, see inline below
On 03/05/2015 10:19, Lalitha Viswanathan wrote:
Hi
I have a dataset of the type attached.
Here's my code thus far.
dataset <-data.frame(read.delim("data", sep="\t", header=TRUE));
newData<-subset(dataset, select = c(Price, Reliability, Mileage, Weight,
Disp, HP));
In fact in the file the variable seems to be called Disp.
cor(newData, method="pearson");
Results are
Price Reliability Mileage Weight Disp
HP
Price 1.0000000 NA -0.6537541 0.7017999 0.4856769
0.6536433
Reliability NA 1 NA NA NA
NA
Mileage -0.6537541 NA 1.0000000 -0.8478541 -0.6931928
-0.6667146
Weight 0.7017999 NA -0.8478541 1.0000000 0.8032804
0.7629322
Disp 0.4856769 NA -0.6931928 0.8032804 1.0000000
0.8181881
HP 0.6536433 NA -0.6667146 0.7629322 0.8181881
1.0000000
It appears that Wt and Price, Wt and Disp, Wt and HP, Disp and HP, HP and
Price are strongly correlated.
To find the statistical significance,
I am trying sample.correln<-cor.test(newData$Disp, newData$HP,
method="kendall", exact=NULL)
Kendall's rank correlation tau
data: newx$Disp and newx$HP
z = 7.2192, p-value = 5.229e-13
alternative hypothesis: true tau is not equal to 0
sample estimates:
tau
0.6563871
If I try the same with
sample.correln<-cor.test(newData$Disp, newData$HP, method="pearson",
exact=NULL)
When I try that it works fine.
The real question is why when you asked it for the Pearson coefficient
it decided to give you the Spearman as the warning message below points
out. I suspect you have done something else which you did not tell us about.
I get Warning message:
In cor.test.default(newx$Disp, newx$HP, method = "spearman", exact = NULL) :
Cannot compute exact p-value with ties
sample.correln
Spearman's rank correlation rho
data: newx$Disp and newx$HP
S = 5716.8, p-value < 2.2e-16
alternative hypothesis: true rho is not equal to 0
sample estimates:
rho
0.8411566
I am not sure how to interpret these values.
Basically, I am trying to figure out which combination of factors
influences efficiency.
Thanks
Lalitha
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Michael
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
