title: One colour gradient according to value in column scatterplot in R
body: <p>I would like to make my scatterplot circles shaded according to the value in one column. </p>
  
  <pre><code>"value"; "avg.sal"; "avg.temp"
  2,5698; 34,27254; 4,44
  5,4361; 34,30686; 4,64
  2,27; 34,3538; 8,05
  5,6015; 34,50136; 5,01
  2,27; 34,37596; 7,4
  </code></pre>
  
  <p>I have my plot ready with salinity on the y-axis and temperature on the x-axis.</p>
  
  <pre><code>plot(df$avg.sal, df$avg.temp)
  </code></pre>
  
  <p>How do I shade the circles (e.g. from light blue to dark blue) according to the column "value"? The values have a big range but smaller values (e.g. 2) should be light blue and larger values (e.g. 10) should be dark blue. I would prefer not to use GGplot.</p>