[amelia] Error in match.fun(FUN) : object 'is' not found

Can anyone help me with this error when trying to run Amelia: I run the same Amelia code (see copied below) fine on my mac, and on my uni's windows 7 computer (both with Amelia 1.7.2. and R 3.0.1). When I try to run the code for several imputation files on our uni's cluster, I get the above error in the output file. I cannot re-create the error on my own computers. The cluster also uses the same R and Amelia version. My code is copied below. Thank you, Nicole Nicole Janz, PhD Cand. Lecturer at Social Sciences Research Methods Centre 2013/14 University of Cambridge Department of Politics and International Studies www.nicolejanz.de | nj248(a)cam.ac.uk | Mobile: +44 (0) 7905 70 1 69 4 Skype: nicole.janz Blog: politicalsciencereplication.wordpress.com Code for imputation (one of 25 for m=1 each): ####################### # Multiple Imputation # Darwin - Janz - original FDI - 1 Year Lag ####################### require(Amelia) #load data set load("t1.Rdata") dim(t1) # 3822 90 colnames(t1) head(t1) t <- t1 # remove unnecessary variables (original FDI) vrm <- c( "Mos_labor", "CIRI_NEW_EMPINX" , "US_fdi_total", "US_fdi_petrol", "US_fdi_total_manuf", "US_fdi_food", "US_fdi_chemical", "US_fdi_prim_fab_metal", "US_fdi_machinery", "US_fdi_electrical" , "US_fdi_transport" , "US_fdi_whole_trade" , "US_fdi_depository" , "US_fdi_finance_except", "US_fdi_mining" , "polity2" , "GDP_const2000" , "GDP_curr" , "WB_FDI_percentGDP" , "WB_FDI_curr" , "population" , "trade" , "confl" , "UN_FDI_flow" , "UN_FDI_flow_pgdp" , "UN_FDI_stock" , "UN_FDI_stock_pgdp" , "l_US_fdi_total" , "l_US_fdi_petrol" , "l_US_fdi_total_manuf" , "l_US_fdi_food" , "l_US_fdi_chemical" , "l_US_fdi_prim_fab_metal", "l_US_fdi_machinery" , "l_US_fdi_electrical" , "l_US_fdi_transport" , "l_US_fdi_whole_trade" , "l_US_fdi_depository" , "l_US_fdi_finance_except", "l_US_fdi_mining" , "l_WB_FDI_percentGDP" , "l_WB_FDI_curr" , "l_UN_FDI_flow" , "l_UN_FDI_flow_pgdp" , "l_UN_FDI_stock" , "l_UN_FDI_stock_pgdp" , "Lag_l_WB_FDI_percentGDP" , "Lag_l_WB_FDI_curr" , "Lag_WB_FDI_percentGDP" , "Lag_WB_FDI_curr" , "Lag_GDP_const2000", "Lag_UN_FDI_flow", "Lag_UN_FDI_flow_pgdp", "Lag_UN_FDI_stock", "Lag_UN_FDI_stock_pgdp" ) length(vrm)#55 t.new <- t[,!(colnames(t) %in% vrm)] dim(t)# 3822 dim(t.new) #3822 37 t <- t.new colnames(t) # Declare log variables that have no negative values vlogs <- c( "Lag_l_US_fdi_mining", #newly inserted "Lag_GDP_curr", "Lag_population", "Lag_trade", "Lag_l_US_fdi_total", "Lag_l_US_fdi_petrol", "Lag_l_US_fdi_total_manuf", "Lag_l_US_fdi_food", "Lag_l_US_fdi_chemical", "Lag_l_US_fdi_prim_fab_metal", "Lag_l_US_fdi_machinery", "Lag_l_US_fdi_electrical", "Lag_l_US_fdi_transport", "Lag_l_US_fdi_whole_trade", "Lag_l_US_fdi_depository", "Lag_l_US_fdi_finance_except", #"Lag_l_US_fdi_mining", "Lag_l_UN_FDI_flow", "Lag_l_UN_FDI_flow_pgdp", "Lag_l_UN_FDI_stock", "Lag_l_UN_FDI_stock_pgdp", "lifeexp", "infmortality" ) set.seed(1004) nmi=1 amelia.out2013.07.10.0004 <- amelia(t, m=nmi, ts="year", cs="country",intercs=TRUE,polytime=1,log=vlogs) # save file save(amelia.out2013.07.10.0004, file="amelia.out2013.07.10.0004.Rdata")