Dear All,

I've tried to sum columns -- different species of flowers, fruits plus twigs -- with NAs to get litterfall/trap, and then after use litterfall to calculate production (litterfall (grams)/ hectare/ day. But R 'sees' litterfall/trap as a string. 

My question: How to use basic mathematical functions to deal with NAs in data management. 

Example (as you can note I have many missing values -- no fruit  fell in the trap.


      area ponto date pseco psaco pliquido florg1 flor1 florg2 flor2 florg3 flor3 frutog1 fruto1 frutog2 fruto2 frutog3 fruto3 frutog4 fruto4 frutog5 fruto5 frutog6 fruto6 frutog7 fruto7 frutog8 fruto8 twigs  
      A A 1 38233 17.7 1.6 7.1 0.266 1                       
      A AA 1 38233 12.5 8.7 3.8                         
      A AB 1 38233 13.9 1.7 3.2       0.421 3                 
      A B 1 38233 12.1 1.6 1.5       0.248 2 0.435 7 0.16 1             
      A BORDA 1 38233                            
      A C 1 38233 15.6 1.7 4.9       0.374 2 0.298 3 0.231 1             
      A F 1 38233 14 1.5 3.5 0.366 45     0.153 1 0.15 1               



Paulo Brando
Inst. de Pesquisa Ambiental da Amazônia (IPAM)
Rua Rui Barbosa,136.
68.005.080 Santarém, PA, Brazil.
Fone/Fax ++ 55 93 522 5538
www.ipam.org.br
	[[alternative HTML version deleted]]


