apply

[Victor Moreno <v.moreno@ico.scs.es>]

I want to count the number of missing cases for each variable in a data.frame

apply( data,2,function(x)sum(is.na(x))) returns always 0
lapply( data,function(x)sum(is.na(x))) returns a list with correct answers
sapply( data,function(x)sum(is.na(x))) returns a vector with correct answers

Why is apply not working in this situation?

-- 
Victor Moreno                                       

V.Moreno@ico.scs.es                                     Victor.Moreno@uab.es
Servei d'Epidemiologia                                  Unitat Bioestadistica, 
Fac. Medicina
Institut Catala d'Oncologia                             Universitat Autonoma de 
Barcelona
Gran Via km 2.7, 08907 Hospitalet,              Cerdanyola, 08193
Barcelona, Spain                                                Barcelona, Spain
Tel +34 93260 7434 / 7401 / 7812                        Tel: +34 93581 2346 / 
1903 
Fax +34 93260 7787                                      Fax +34 93581 2344