title: R-invalid multibyte string 1
body: <p>I'm new to R software</p>
  
  <p>Now,studying text mining using "tm"package"</p>
  
  <p>I have a ploblem on mapping text to lower case</p>
  
  <pre><code>sms_raw&lt;-read.csv(............)
  sms_corpus&lt;-Corpus(VectorSource(sms_raw$text)) 
  sms_corpus&lt;-Corpus(VectorSource(sms_raw$text))  
  tm_map(sms_corpus,content_transformer(tolower))   
  error:invalid multubytes string 1
  </code></pre>
  
  <p>I thought my csv file could be not utf-8 so I restored as utf-8 but it didn't work.</p>
  
  <p>my OS is win8.1</p>
  
  <p>Anyone have solution on this problem please let me know.</p>