Suppose you have the following dataframe:

df <- data.frame(industry = c("DEU_10T12", "DEU_13T15", "DEU_16", "DEU_17", "ITA_10T12", "ITA_13T15", "ITA_16", "ITA_17"),
DEU_10T12 = c(20, 24, 26, 20, 10, 0, NA, 1.5),DEU_13T15 = c(15, 16, 4.5, NA, 7.5, 5, 3, 0),
DEU_16 = c(1.5, 6, 4, 0, 0.5, 15, 3, 0.5),DEU_17 = c(NA, 20, 10, 2, 0, 0, 0, 7),
ITA_10T12 = c(0.5, 2, 3, 4, 10, 50, 2, 15), ITA_13T15 = c(25, 0, 4.5, NA, 17.5, 5, 13, 0.9),
ITA_16 = c(2, 3, 40, 20, 0.5, 15, 3, 1),ITA_17 = c(1, 9, 0.5, 2, 10, 20, 50, 7))

And the objective is to have the following matrix (it shall be numeric and handle NAs summation):

df2 <- data.frame(industry = c("DEU_10T12", "DEU_13T15", "DEU_16", "DEU_17", "ITA_10T12", "ITA_13T15", "ITA_16", "ITA_17"),
DEU_10T12 = c(0, 0, 0, 0, 10, 0, NA, 1.5),DEU_13T15 = c(0, 0, 0, 0, 7.5, 5, 3, 0),
DEU_16 = c(0, 0, 0, 0, 0.5, 15, 3, 0.5),DEU_17 = c(0, 0, 0, 0, 0, 0, 0, 7),
ITA_10T12 = c(0.5, 2, 3, 4, 0, 0, 0, 0),  ITA_13T15 = c(25, 0, 4.5, NA, 0, 0, 0, 0),
ITA_16 = c(2, 3, 40, 20, 0, 0, 0, 0),ITA_17 = c(1, 9, 0.5, 2, 0, 0, 0, 0))

The new matrix (df2, converted to numeric) will mirror the values of the original matrix (df, also numeric), except when a row entry shares the same initial three digits as its corresponding column entry. In such cases, like for example DEU_10T12 in row and a column starting with DEU, the value will be set to zero, disregarding any existing NA values.

I tried as follows. First, I transform df as numeric as follows

# Extract row and column names
row_names <- df$industry
col_names <- colnames(df)[-1]  # Exclude 'industry' column

# Create an empty matrix
Z <- matrix(NA, nrow = length(row_names), ncol = length(col_names), dimnames = list(row_names, col_names))

# Fill in the matrix with values from the data frame
for (i in 1:length(row_names)) {
for (j in 1:length(col_names)) {
Z[i, j] <- df[i, col_names[j]]
}
}

# Create an empty matrix for Z_narrow
Z_narrow = matrix(0, nrow = nrow(Z), ncol = ncol(Z))
# Assign row and column names
rownames(Z_narrow) = rownames(Z)
colnames(Z_narrow) = colnames(Z)

# Function to get the indices of columns to be replaced with zeros based on the first three characters of the column name
get_zero_indices <- function(col_name, row_names) {substr(col_name, 1, 3) == substr(row_names, 1, 3)}


# Loop through each row of Z to populate Z_narrow
for (i in 1:nrow(Z)) {
row_name <- rownames(Z)[i]
indices_to_zero <- sapply(colnames(Z), get_zero_indices, row_names = row_name)
Z_narrow[i, indices_to_zero] <- 0
Z_narrow[i, !indices_to_zero] <- Z[i, !indices_to_zero]
}

This code works when using this little dataset, but it causes R to crash when applied to a larger dataset. Any suggestions?