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weights.matrix <- function(match.matrix, treat, discarded){
n <- length(treat)
labels <- names(treat)
tlabels <- labels[treat==1]
clabels <- labels[treat==0]
in.sample <- !discarded
names(in.sample) <- labels
match.matrix <- match.matrix[tlabels,,drop=F][in.sample[tlabels],,drop=F]
num.matches <- dim(match.matrix)[2]-apply(as.matrix(match.matrix),
1, function(x){sum(is.na(x))})
names(num.matches) <- tlabels[in.sample[tlabels]]
t.units <- row.names(match.matrix)[num.matches>0]
c.units <- na.omit(as.vector(as.matrix(match.matrix)))
weights <- rep(0,length(treat))
names(weights) <- labels
weights[t.units] <- 1
for (cont in clabels) {
treats <- na.omit(row.names(match.matrix)[cont==match.matrix[,1]])
if (dim(match.matrix)[2]>1)
for (j in 2:dim(match.matrix)[2])
treats <- c(na.omit(row.names(match.matrix)[cont==match.matrix[,j]]),treats)
for (k in unique(treats))
weights[cont] <- weights[cont] + 1/num.matches[k]
}
if (sum(weights[clabels])==0)
weights[clabels] <- rep(0, length(weights[clabels]))
else
weights[clabels] <- weights[clabels]*length(unique(c.units))/sum(weights[clabels])
weights[!in.sample] <- 0
if (sum(weights)==0)
stop("No units were matched")
else if (sum(weights[tlabels])==0)
stop("No treated units were matched")
else if (sum(weights[clabels])==0)
stop("No control units were matched")
return(weights)
}
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