title: increase polyline length r sf
body: <p>I'd like to find a way to increase a polyline 1000 feet from the beginning and 1000 feet from the end points. Any help is greatly appreciated! Below is a sample.</p>
  <pre><code>structure(
      list(
          TECHNICAL_ = NA_character_,
          geometry = structure(
              list(
                  structure(
                      c(812697.360851467,
                        813792.18162311,
                        430678.939150205,
                        425750.102767913),
                      .Dim = c(2L, 2L),
                      class = c(&quot;XY&quot;, &quot;LINESTRING&quot;, &quot;sfg&quot;)
                  )
              ),
              n_empty = 0L,
              crs = structure(
                  list(
                      input = &quot;+init=epsg:2257&quot;,
                      wkt = &quot;PROJCRS[\&quot;NAD83 / New Mexico East (ftUS)\&quot;,\n    BASEGEOGCRS[\&quot;NAD83\&quot;,\n        DATUM[\&quot;North American Datum 1983\&quot;,\n            ELLIPSOID[\&quot;GRS 1980\&quot;,6378137,298.257222101,\n                LENGTHUNIT[\&quot;metre\&quot;,1]]],\n        PRIMEM[\&quot;Greenwich\&quot;,0,\n            ANGLEUNIT[\&quot;degree\&quot;,0.0174532925199433]],\n        ID[\&quot;EPSG\&quot;,4269]],\n    CONVERSION[\&quot;SPCS83 New Mexico East zone (US Survey feet)\&quot;,\n        METHOD[\&quot;Transverse Mercator\&quot;,\n            ID[\&quot;EPSG\&quot;,9807]],\n        PARAMETER[\&quot;Latitude of natural origin\&quot;,31,\n            ANGLEUNIT[\&quot;degree\&quot;,0.0174532925199433],\n            ID[\&quot;EPSG\&quot;,8801]],\n        PARAMETER[\&quot;Longitude of natural origin\&quot;,-104.333333333333,\n            ANGLEUNIT[\&quot;degree\&quot;,0.0174532925199433],\n            ID[\&quot;EPSG\&quot;,8802]],\n        PARAMETER[\&quot;Scale factor at natural origin\&quot;,0.999909091,\n            SCALEUNIT[\&quot;unity\&quot;,1],\n            ID[\&quot;EPSG\&quot;,8805]],\n        PARAMETER[\&quot;False easting\&quot;,541337.5,\n            LENGTHUNIT[\&quot;US survey foot\&quot;,0.304800609601219],\n            ID[\&quot;EPSG\&quot;,8806]],\n        PARAMETER[\&quot;False northing\&quot;,0,\n            LENGTHUNIT[\&quot;US survey foot\&quot;,0.304800609601219],\n            ID[\&quot;EPSG\&quot;,8807]],\n        ID[\&quot;EPSG\&quot;,15339]],\n    CS[Cartesian,2],\n        AXIS[\&quot;(E)\&quot;,east,\n            ORDER[1],\n            LENGTHUNIT[\&quot;US survey foot\&quot;,0.304800609601219,\n                ID[\&quot;EPSG\&quot;,9003]]],\n        AXIS[\&quot;(N)\&quot;,north,\n            ORDER[2],\n            LENGTHUNIT[\&quot;US survey foot\&quot;,0.304800609601219,\n                ID[\&quot;EPSG\&quot;,9003]]],\n    USAGE[\n        SCOPE[\&quot;unknown\&quot;],\n        AREA[\&quot;USA - New Mexico - SPCS - E\&quot;],\n        BBOX[32,-105.72,37,-102.99]]]&quot;
                  ),
                  class = &quot;crs&quot;
              ),
              class = c(&quot;sfc_LINESTRING&quot;, &quot;sfc&quot;),
              precision = 0,
              bbox = structure(
                  c(xmin = 812697.360851467,
                    ymin = 425750.102767913,
                    xmax = 813792.18162311,
                    ymax = 430678.939150205),
                  class = &quot;bbox&quot;
              )
          )
      ),
      row.names = 1L,
      sf_column = &quot;geometry&quot;,
      agr = structure(c(TECHNICAL_ = NA_integer_),
                      .Label = c(&quot;constant&quot;, &quot;aggregate&quot;, &quot;identity&quot;),
                      class = &quot;factor&quot;),
      class = c(&quot;sf&quot;, &quot;tbl_df&quot;, &quot;tbl&quot;, &quot;data.frame&quot;)
  )
  </code></pre>