title: How to plot multiple columns in R for the same X-Axis Value
body: <p>I need to plot three values, to make three bars for each value of the X-Axis. My data is:
  <img src="https://i.stack.imgur.com/5Ybls.png" alt="My dataframe DF"></p>
  
  <p>In the X-Axis must be the column labeled as "m" and for each "m" value I need to plot the correspondent "x","y" and "z" value.</p>
  
  <p>I want to use ggplot2 and I need something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/bNCJ8.png" alt="Goal"></p>