title: how to filter a set of rownames that have a certain sequence of characters, using dplyr in R?
body: <p>I have it:</p>
  <pre><code>mtcars
                       mpg cyl  disp  hp drat    wt  qsec vs am gear carb
  Mazda RX4           21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
  Mazda RX4 Wag       21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
  Datsun 710          22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
  Hornet 4 Drive      21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
  Hornet Sportabout   18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
  Valiant             18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1
  Duster 360          14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4
  Merc 240D           24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
  Merc 230            22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
  Merc 280            19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
  Merc 280C           17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
  Merc 450SE          16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
  Merc 450SL          17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
  Merc 450SLC         15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
  Cadillac Fleetwood  10.4   8 472.0 205 2.93 5.250 17.98  0  0    3    4
  Lincoln Continental 10.4   8 460.0 215 3.00 5.424 17.82  0  0    3    4
  </code></pre>
  <p>Output:</p>
  <pre><code>&gt; mtcars %&gt;% filter(rownames(mtcars) %in% &quot;^M&quot;)
   [1] mpg  cyl  disp hp   drat wt   qsec vs   am   gear carb
  &lt;0 linhas&gt; (ou row.names de comprimento 0)
  </code></pre>
  <p>expected output:</p>
  <pre><code>mtcars
                       mpg cyl  disp  hp drat    wt  qsec vs am gear carb
  Mazda RX4           21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
  Mazda RX4 Wag       21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
  Merc 240D           24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2
  Merc 230            22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2
  Merc 280            19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4
  Merc 280C           17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4
  Merc 450SE          16.4   8 275.8 180 3.07 4.070 17.40  0  0    3    3
  Merc 450SL          17.3   8 275.8 180 3.07 3.730 17.60  0  0    3    3
  Merc 450SLC         15.2   8 275.8 180 3.07 3.780 18.00  0  0    3    3
  </code></pre>
  <p>I only found solutions when the column is string.</p>
  <p>In this case, the search must be performed on rownames.</p>