[R] z-test with NAs

ms.com loginms at hotmail.com
Fri Nov 13 11:59:38 CET 2009


Dear all
I am learning R
I am doing Z-test with package 'BSDA'
here is my syntax and result:

> sdgr.ztest<-z.test(growth[type=='SD'& from_treeline=='above'], +   growth[type=='SD'& from_treeline=='below'],alternative = "two.sided", +   mu = 0, sigma.x =(sd(growth[type=='SD'& from_treeline=='above'],na.rm = T)), +   sigma.y =(sd(growth[type=='SD'& from_treeline=='below'],na.rm = T)), conf.level = 0.95)> sdgr.ztest # Z-test for Seedling Growth above and below treeline
        Two-sample z-Test
data:  growth[type == "SD" & from_treeline == "above"] and growth[type == "SD" & from_treeline == "below"] z = NA, p-value = NAalternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: NA NA sample estimates:mean of x mean of y        NA        NA 

I don't understand where my syntax went wrong. Similar syntax works for sapling case, but not for seedling case. is it due to the NAs in my data set for seedlings?, as the package says, NAs are allowed but will be removed during analysis, i don't think it is the problem.
i am attaching the data file too. and one more information, I am using MS Windows 2003 OS. 
Please guide me, how can i go ahead.

Thanking you in anticipation 

Warm regard
MS
Madan
 

 		 	   		  
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