extracting values of a column into a string and replacing values in a data frame column - r

Question

More than the programming, I am lost on the right approach for this problem. I have 2 data frames with a market name column. Unfortunately the names vary by a few characters / symbols in each column, for e.g. Albany.Schenectady.Troy = ALBANY, Boston.Manchester = BOSTON.
I want to standardize the market names in both data frames so I can perform merge operations later.
I thought of tackling the problem in two steps:
1) Create a vector of the unique market names from both tables and use that to create a look up table. Something that looks like:
Table 1 Markets > "Albany.Schenectady.Troy" , "Albuquerque.Santa.Fe", "Atlanta" . . . .
Table2 Markets > "SPOKANE" , "BOSTON" . . .
I tried marketnamesvector <- paste(unique(Table1$Market, sep = "", collapse = ",")) but that doesn't produce the desired output.
2) Change Market names in Table 2 to equivalent market names in Table 1. For any market name not available in Table 1, Table 2 should retain the same value in market name.
I know I could use a looping function like below but I still need a lookup table I think.
replacefunc <- function (data, oldvalue, newvalue) {
newdata <- data
for (i in unique(oldvalue)) newdata[data == i] <- newvalue[oldvalue == i]
newdata
}
Table 1: This table is 90 rows x 2 columns and has 90 unique market names.
Market Leads Investment Leads1 Leads2 Leads3
1 Albany.Schenectady.Troy NA NA NA NA NA
2 Albuquerque.Santa.Fe NA NA NA NA NA
3 Atlanta NA NA NA NA NA
4 Austin NA NA NA NA NA
5 Baltimore NA NA NA NA NA
Table 2 : This table is 150K rows x 20 columns and has 89 unique market names.
> df
Spot.ID Date Hour Time Local.Date Broadcast.Week Local.Hour Local.Time Market
2 13072765 6/30/14 0 12:40 AM 2014-06-29 1 21 9:40 PM SPOKANE
261 13072946 6/30/14 5 5:49 AM 2014-06-30 1 5 5:49 AM BOSTON
356 13081398 6/30/14 10 10:52 AM 2014-06-30 1 7 7:52 AM SPOKANE
389 13082306 6/30/14 11 11:25 AM 2014-06-30 1 8 8:25 AM SPOKANE
438 13082121 6/30/14 8 8:58 AM 2014-06-30 1 8 8:58 AM BOSTON
469 13081040 6/30/14 9 9:17 AM 2014-06-30 1 9 9:17 AM ALBANY
482 13080104 6/30/14 12 12:25 PM 2014-06-30 1 9 9:25 AM SPOKANE
501 13082120 6/30/14 9 9:36 AM 2014-06-30 1 9 9:36 AM BOSTON
617 13080490 6/30/14 13 1:23 PM 2014-06-30 1 10 10:23 AM SPOKANE

Answer 1

Assume that the data is in data frames df1, df2. The goal is to adjust the market names to be the same, they are currently slightly different.
First, list the markets, use the following command to list the unique names in df1, repeat for df2.
mk1 <- sort(unique(df1$market))
mk2 <- sort(unique(df2$market))
dmk12 <- setdiff(mk1,mk2)
dmk21 <- setdiff(mk2,mk1)
Use dmk12 and dmk21 to identify the different markets. Decide what names to use, and how they match up, let's change "Atlanta, GA" from df1 to "Atlanta" from df2. Then use
df2[df2$market=="Atlanta","market"] = "Atlanta, GA"
The format is
df_to_change[df_to_change[,"column"]=="old data", "column"] = "new data"
If you only have 90 names to correct, I would write out 90 change lines like the one above.
After adjusting all the names, do sort(unique(df)) again and use setdiff twice to confirm all the names are the same.