[R-meta] Zero seTE in network MA

Guido Schwarzer sc at imbi.uni-freiburg.de
Fri Sep 22 17:53:38 CEST 2017

Dear Carla,

I discussed the check for zero treatment arm variances with Gerta. We 
realized that we have been overcautious with respect to zero treatment 
arm variances which can happen in real live (as your example nicely 
shows). We changed the behaviour of netmeta() such that a warning 
instead of an error is triggered for zero treatment arm variances 
(similar to the warning for re-ordering of treatment arms).

This change is implemented in the development version of *netmeta* 
available on GitHub:

devtools::install_github("guido-s/netmeta", ref = "develop")

In your second example, treatment effects are inconsistent as you missed 
a minus sign for the comparison exotic.forest vs forest.harvested (see 
attached R code). ;-)

Best wishes,

Dr. Guido Schwarzer (sc at imbi.uni-freiburg.de)
Institute for Medical Biometry and Statistics
Stefan-Meier-Str. 26, D-79104 Freiburg | Phone: +49 (0)761 203 6668
http://www.imbi.uni-freiburg.de        | Fax:   +49 (0)761 203 6680

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## Read dataset with wrong comparison for 'Exotic forest' vs 'Harvested forest'
example <- read.csv("example.csv")

## Correct dataset
example.corrected <- example
example.corrected$TE[4] <- -example.corrected$TE[4]

options(width = 120)

## Use corrected dataset
netmeta(TE,seTE,treat1, treat2, studlab, data = example.corrected,
        comb.random = TRUE, sm="Log response ratio", details.chkmultiarm=TRUE,
        ref = "forest.harvested")

## Just 1 study
netmeta(TE,seTE,treat1, treat2, studlab, data = example.corrected[-1, ],
        comb.random = TRUE, sm="Log response ratio", details.chkmultiarm=TRUE,
        ref = "forest.harvested")

## Error ...
netmeta(TE,seTE,treat1, treat2, studlab, data = example,
        comb.random = TRUE, sm="Log response ratio", details.chkmultiarm=TRUE)
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