从mysql提取C50算法后，将数据帧的所有列编码为R中的UTF-8

我正面临一个奇怪的问题，我希望它与utf-8有关。如果我错了，请纠正我

我从mysql中提取数据，如下所示

library(C50)
library(RMySQL)
library(DBI)
fetchRecordsQuery<-"SELECT PRODUCT_CODE as PRODUCT_CODE,SUPPLIER_NAME as SUPPLIER_NAME,taxonomy_level1_name as taxonomy_level1_name,taxonomy_level2_name as taxonomy_level2_name,taxonomy_level3_name as taxonomy_level3_name FROM  EVPI_SanityRulesPredict_111.Invoice_111_orig WHERE is_classified=1 LIMIT 30000 OFFSET 0"
connection <- dbConnect(MySQL(), user=userName, password=userPassword, dbname=databaseName, host=hostName, port=as.integer(port))setNamesQuery<-"SET NAMES utf8"
setNamesQuery<-"SET NAMES utf8"
rs <- dbSendQuery(connection, setNamesQuery)
rs <- dbSendQuery(connection, fetchRecordsQuery)
c50data <- fetch(rs, n=-1)

等等

如果与编码相关，那么如何将整个数据集转换为UTF-8？

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请帮我解决这个问题。提前感谢

？感谢@Xizam的评论。我尝试使用c50data$SUPPLIER_NAME更改数据框中各个列的编码？谢谢@Xizam的评论。我已尝试使用c50data$SUPPLIER\u NAME更改数据帧各个列的编码

ruleModel <- C5.0(as.formula(frmla), data=c50data, rules=TRUE)

*** line 1 of `undefined.data': bad value of `▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒' for attribute `SUPPLIER_NAME'
*** line 2 of `undefined.data': bad value of `▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒' for attribute `SUPPLIER_NAME'