title: Find lat/lon within a radius from a known centered point in R
body: <p>I have a known point (centre) with known latitude and longitude and I have some coordinates (in lat/lon) in a df and I want to see which ones are within a radius of 5km or less from the centre point.</p>
  
  <p>Centre</p>
  
  <pre><code>mylon &lt;- c(-2.106472)
  mylat &lt;- c(57.14455)
  </code></pre>
  
  <p>Coordinates</p>
  
  <pre><code>longitude latitude
   [1,] -2.141177 57.16278
   [2,] -2.090960 57.18079
   [3,] -2.118894 57.12292
   [4,] -2.140090 57.13763
   [5,] -2.113988 57.13855
   [6,] -2.123892 57.13585
   [7,] -2.144685 57.17207
   [8,] -2.220046 57.19150
   [9,] -2.114343 57.09301
  [10,] -2.285314 57.20138
  [11,] -2.092354 57.14279
  [12,] -2.149571 57.15334
  [13,] -2.126605 57.15615
  [14,] -2.097045 57.10443
  [15,] -2.183441 57.15051
  [16,] -2.166915 57.15089
  [17,] -2.133863 57.15201
  [18,] -2.100909 57.18968
  [19,] -2.106770 57.15670
  [20,] -2.251495 57.19315
  [21,] -2.118894 57.12292
  [22,] -2.140090 57.13763
  [23,] -2.123201 57.12686
  [24,] -2.114343 57.09301
  [25,] -2.140327 57.15676
  [26,] -2.148826 57.17355
  [27,] -2.120553 57.12507
  [28,] -2.133902 57.16279
  [29,] -2.094246 57.17180
  [30,] -2.113170 57.14125
  [31,] -2.251495 57.19315
  [32,] -2.090960 57.18079
  [33,] -2.212955 57.10941
  [34,] -2.118894 57.12292
  [35,] -2.183501 57.19596
  [36,] -2.140090 57.13763
  [37,] -2.249217 57.10063
  [38,] -2.123201 57.12686
  [39,] -2.114343 57.09301
  [40,] -2.092354 57.14279
  [41,] -2.148826 57.17355
  [42,] -2.120553 57.12507
  [43,] -2.117338 57.15301
  [44,] -2.116486 57.14484
  [45,] -2.094981 57.13614
  [46,] -2.232998 57.14629
  [47,] -2.118894 57.12292
  [48,] -2.140090 57.13763
  [49,] -2.123201 57.12686
  [50,] -2.104092 57.14485
  [51,] -2.114343 57.09301
  [52,] -2.148826 57.17355
  [53,] -2.175179 57.15079
  [54,] -2.090713 57.14755
  [55,] -2.090960 57.18079
  [56,] -2.118894 57.12292
  [57,] -2.140090 57.13763
  </code></pre>
  
  <p>I would appreciate any help. Thanks a lot </p>