title: Removing levels in data frame when importing csv data
body: <p>I am importing csv data to R using </p>
  
  <pre><code>data &lt;- read.csv(file="file_name.csv")
  </code></pre>
  
  <p>This data has 9 columns and 5000 rows and data values are real number. Now I want to use this data as a data frame. But the first columns occurs with some levels. I don't want this levels.</p>
  
  <p>Here is a sample data in .csv format</p>
  
  <p><img src="https://i.stack.imgur.com/6M5Cn.png" alt="enter image description here"></p>
  
  <p>Could any one please help me to remove the levels from the first column after it is imported to R.</p>
  
  <p>Here is my attempt:</p>
  
  <pre><code>data$col_1 = as.numeric(as.character(data$col_1))
  </code></pre>
  
  <p>But it showing warning: </p>
  
  <pre><code>Warning message:
  NAs introduced by coercion 
  </code></pre>