[R] Error message in meta-analysis package Metafor-weights =""

[K Amoatwi]

Dear All,
I am using the example from one of the tutorial about "Metafor" package and
"escalc" function, to learn how this package can be applied to do
meta-analysi; the code and the data is directly from the tutorials but
"weights=freq" option in the escalc function is given me error message
This is the code below:

library(metafor) # Load package
#####DATASET 1: BCG Vaccine Trials
data(dat.bcg) # BCG meta-analytic dataset

##Formula based Specification
##That is, what if I have multiple rows per study, corresponding to
difference treatment groups?

library(reshape2) # Load package for data reshaping

bcg.long <- melt(dat.bcg[, c("trial", "tpos", "tneg", "cpos", "cneg")], id
= "trial")
bcg.long$pos <- ifelse(bcg.long$var == "tpos" | bcg.long$var == "cpos", 1,
0)
bcg.long$group <- ifelse(bcg.long$var == "tpos" | bcg.long$var == "tneg",
1, 0)

##sample of the data, the first 6 rows
head(bcg.long)
  trial variable value pos group
1     1     tpos     4     1     1
2     2     tpos     6     1     1
3     3     tpos     3     1     1
4     4     tpos    62    1     1
5     5     tpos    33    1     1
6     6     tpos   180   1     1

##Now applying the " escalc " function

escalc(factor(pos)~factor(group)| factor(trial),weights = value,data =
bcg.long, measure = "OR")

##Then I got this error message
Error in escalc(factor(pos) ~ factor(group) | factor(trial), weights =
value,  :
  object 'value' not found

I used the same data with different example from another author and got a
similar error message
Second code with the same data but different coding
Sample data

with the first 6 rows of the rearranged data shown below. (T=treatment,
C=Control group, Out=outcome whether positive or negative, and then
frequency)
    study grp out freq
1        1    T    +      4
2        1    T    -    119
3        1    C   +      11
4        1    C   -     128
5        2    T   +        6
6        2    T   -      300

>escalc(out ~ grp | study, weights = freq, data = dat.fm, measure = "OR")

Error in escalc(out ~ grp | study, weights = freq, data = dat.fm, measure =
"OR") :
  object 'freq' not found

I am not sure what I am doing wrong since both authors were able to get
their results while I am getting error messages.

Any help will be very much appreciated

Amoatwi

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