/font>'.  Other columns
are: `<font color="#82140F"><code>z</code></font>', used for contouring a function `<font color="#82140F"><code>z=z(x,y)</code></font>';
`<font color="#82140F"><code>weight</code></font>', used for weighting data points; `<font color="#82140F"><code>u</code></font>' and `<font color="#82140F"><code>v</code></font>',
used for arrow (vector) plots.
<p>
If the keyword `<font color="#82140F"><code>appending</code></font>' is given as the last word on the
`<font color="#82140F"><code>read