[R] Distance in miles btw Zipcodes

[Farnoosh Sheikhi]

 Hello,
I'm trying to get the distances between two Zipcode variables, but for some reason I get this error:
"matching was not perfect, returning what was found.Error: no such index at level 1"
Here is my code:

library(ggmap)mapdist(data$Zip.A, data$Zip.B, mode = "driving")
The Zip codes are all in 5 digits format.I really appreciate any help or suggestion.Thanks.

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