我想对多列中的大量变量进行重新编码。下面是一个df示例
df <- data.frame(
id_number = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
age = c(10, 11, 12, 13, 14, 15, 16, 17, 18, 19),
abc1 = c(501, 502, 503, 504, 505, 506, 507, 508, 509, 510),
abc2 = c(501, 502, 501, 501, 502, 501, 502, 503, 501, 502),
abc3 = c(501, 506, 501, 50