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October 1, 2015 19:10
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This code takes a lookup table and applies it to a data frame, updating only values for records that occur in the lookup table using indexing and match
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| # Create data frame 1 | |
| x = c("ID1","ID2","ID3","ID4","ID5") | |
| y = c("C1","C2","C3","C4","C5") | |
| d1 = data.frame("SiteID" = x, "Value" = y) | |
| d1 | |
| # Create lookup table | |
| x = c("ID2","ID5") | |
| y = c("C5","C2") | |
| lookup = data.frame("SiteID" = x, "Value" = y) | |
| lookup | |
| # Now update the values in data frame just for SiteIDs in the lookup table | |
| d1$Value[d1$SiteID %in% lookup$SiteID] = | |
| lookup$Value[match(d1$SiteID[d1$SiteID %in% lookup$SiteID],lookup$SiteID)] | |
| d1 |
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