title: R ggplot group by date and plot time in the x axis from the same datetime
body: <p>I have a <code>df</code> with an integer variable, <code>counts</code>, and a POSIXct <code>datetime</code> variable. The datetime variable represents minute intervals of different days:</p>
  
  <pre><code>counts  datetime
  246 02/11/2011 19:00
  237 02/11/2011 19:01
  268 02/11/2011 19:02
  496 02/11/2011 19:03
  259 02/11/2011 19:04
  
  548 09/12/2011 20:14
  </code></pre>
  
  <p>I would like to have a line plot for each day, with the different HH:MM in the x axis. I can get the day, hours and minutes with <code>lubridate</code>:</p>
  
  <pre><code>require(lubridate)
  day(df$datetime)
  minute(df$datetime)
  </code></pre>
  
  <p>But I am unable to put them together (I have tried the route of turning datetime to a HH:MM character unsuccessfully). I am missing the "x=factor(HH:MM of datetime)" below. Any idea comment?</p>
  
  <pre><code>ggplot(df, aes(x=factor(HH:MM of datetime), y=counts, group=day(datetime)) + geom_line()
  </code></pre>
  
  <p>Example: Each line should a different day. The x axis should be the HH:MM, the y the counts. 
  <img src="https://i.stack.imgur.com/yQNcH.png" alt="Example"></p>
  
  <p>Data:</p>
  
  <pre><code>structure(list(all = c(246, 237, 268, 496, 259, 294, 414, 290, 
  267, 375, 402, 355, 572, 319, 354, 612, 478, 327, 511, 500, 468, 
  565, 472, 524, 844, 442, 382, 515, 542, 390, 511, 759, 933, 805, 
  774, 660, 748, 645, 501, 775, 768, 416, 612, 748, 554, 832, 1106, 
  760, 1127, 995, 846, 1057, 1287, 866, 923, 1264, 1017, 755, 1102, 
  753, 968, 1245, 943, 1013, 1324, 1515, 1098, 1160, 1656, 1209, 
  1434, 1330, 1248, 1558, 1406, 1689, 1584, 1543, 1405, 1907, 1606, 
  1353, 2332, 1861, 1653, 2396, 1894, 1730, 2620, 1795, 1940, 2186, 
  2443, 2234, 2618, 2397, 2122, 2410, 2835, 2325, 2456, 2484, 2375, 
  2515, 2679, 2833, 2476, 3362, 2629, 3262, 3070, 2683, 2882, 3190, 
  2523, 3286, 2988, 2724, 2897, 2917, 2630, 2990, 2399, 2329, 2571, 
  2361, 2162, 2206, 2008, 2243, 2494, 1869, 1807, 2316, 2381, 1803, 
  2396, 1850, 1872, 2156, 1739, 1722, 2094, 1462, 1891, 1980, 1303, 
  1640, 1659, 1217, 1236, 1323, 1127, 1314, 1551, 1169, 1405, 1284, 
  1120, 1306, 1424, 971, 1068, 1375, 1198, 1123, 1202, 1007, 988, 
  1195, 1087, 953, 1070, 1050, 764, 913, 813, 862, 1058, 844, 329, 
  299, 236, 462, 330, 264, 339, 388, 220, 443, 451, 407, 393, 289, 
  367, 482, 506, 367, 565, 604, 459, 615, 555, 485, 633, 411, 430, 
  341, 719, 619, 477, 903, 785, 713, 765, 607, 782, 799, 551, 706, 
  682, 447, 664, 1223, 609, 797, 957, 799, 815, 924, 889, 1133, 
  1114, 820, 857, 1236, 1007, 753, 1276, 966, 950, 1345, 1131, 
  1030, 1626, 828, 1358, 1469, 1267, 1232, 1462, 1419, 1461, 1736, 
  1470, 1281, 2091, 1797, 1247, 1731, 1512, 1460, 2199, 1691, 1890, 
  2229, 2128, 2107, 2623, 1875, 2163, 2057, 2626, 1914, 2312, 2229, 
  2362, 2234, 2674, 1745, 2995, 2709, 2150, 2666, 2450, 2363, 2610, 
  3050, 2975, 2861, 3075, 2638, 3136, 3272, 2440, 2874, 2904, 2716, 
  3124, 3056, 2413, 2916, 2057, 2384, 2649, 2304, 2034, 2246, 2360, 
  2324, 2566, 1972, 1986, 2430, 2150, 1853, 2067, 1900, 1778, 2091, 
  1936, 1749, 1906, 1789, 1656, 1998, 1463, 1449, 1534, 1252, 1515, 
  1704, 1440, 1397, 1521, 1155, 1320, 1281, 1033, 1229, 1369, 989, 
  1239, 1154, 1079, 924, 1168, 1008, 1127, 1186, 991, 921, 1174, 
  991, 799, 694, 1037, 1033, 962, 874, 417, 114, 263, 499, 297, 
  292, 424, 376, 270, 396, 382, 300, 523, 352, 236, 590, 613, 355, 
  608, 527, 357, 594, 491, 423, 796, 478, 433, 491, 547, 303, 485, 
  611, 378, 940, 863, 475, 650, 855, 868, 903, 561, 551, 521, 1084, 
  820, 690, 1040, 759, 1024, 896, 499, 1022, 1153, 697, 1208, 802, 
  745, 1242, 1070, 1039, 1020, 1204, 1127, 997, 1491, 993, 1270, 
  1390, 1014, 1233, 1525, 1098, 954, 1581, 1751, 1379, 1669, 1875, 
  1742, 1195, 2002, 1715, 1891, 1581, 1441, 1889, 2346, 1838, 2400, 
  1955, 2344, 2027, 2057, 1744, 2436, 2328, 2191, 1899, 2942, 2348, 
  2871, 2691, 2773, 2592, 2961, 2811, 2517, 2850, 2739, 2814, 2998, 
  2726, 2969, 3176, 2785, 3039, 2817, 2778, 3290, 2653, 2495, 2622, 
  2553, 2549, 2398, 2161, 2121, 2401, 2504, 2289, 2418, 2238, 2077, 
  2288, 2062, 2033, 2081, 2096, 1722, 1942, 1772, 1800, 1731, 1424, 
  1821, 2101, 1454, 1533, 1585, 1680, 1522, 1547, 1335, 1614, 1557, 
  1389, 1369, 1412, 1294, 1351, 1417, 1395, 997, 1092, 1296, 1050, 
  1023, 1229, 1025, 1271, 745, 994, 1078, 1020, 1074, 776, 578, 
  1044, 1107, 966), datetime = structure(c(1265176800, 1265176860, 
  1265176920, 1265176980, 1265177040, 1265177100, 1265177160, 1265177220, 
  1265177280, 1265177340, 1265177400, 1265177460, 1265177520, 1265177580, 
  1265177640, 1265177700, 1265177760, 1265177820, 1265177880, 1265177940, 
  1265178000, 1265178060, 1265178120, 1265178180, 1265178240, 1265178300, 
  1265178360, 1265178420, 1265178480, 1265178540, 1265178600, 1265178660, 
  1265178720, 1265178780, 1265178840, 1265178900, 1265178960, 1265179020, 
  1265179080, 1265179140, 1265179200, 1265179260, 1265179320, 1265179380, 
  1265179440, 1265179500, 1265179560, 1265179620, 1265179680, 1265179740, 
  1265179800, 1265179860, 1265179920, 1265179980, 1265180040, 1265180100, 
  1265180160, 1265180220, 1265180280, 1265180340, 1265180400, 1265180460, 
  1265180520, 1265180580, 1265180640, 1265180700, 1265180760, 1265180820, 
  1265180880, 1265180940, 1265181000, 1265181060, 1265181120, 1265181180, 
  1265181240, 1265181300, 1265181360, 1265181420, 1265181480, 1265181540, 
  1265181600, 1265181660, 1265181720, 1265181780, 1265181840, 1265181900, 
  1265181960, 1265182020, 1265182080, 1265182140, 1265182200, 1265182260, 
  1265182320, 1265182380, 1265182440, 1265182500, 1265182560, 1265182620, 
  1265182680, 1265182740, 1265182800, 1265182860, 1265182920, 1265182980, 
  1265183040, 1265183100, 1265183160, 1265183220, 1265183280, 1265183340, 
  1265183400, 1265183460, 1265183520, 1265183580, 1265183640, 1265183700, 
  1265183760, 1265183820, 1265183880, 1265183940, 1265184000, 1265184060, 
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  1265184480, 1265184540, 1265184600, 1265184660, 1265184720, 1265184780, 
  1265184840, 1265184900, 1265184960, 1265185020, 1265185080, 1265185140, 
  1265185200, 1265185260, 1265185320, 1265185380, 1265185440, 1265185500, 
  1265185560, 1265185620, 1265185680, 1265185740, 1265185800, 1265185860, 
  1265185920, 1265185980, 1265186040, 1265186100, 1265186160, 1265186220, 
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  1265266920, 1265266980, 1265267040, 1265267100, 1265267160, 1265267220, 
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  1265271240, 1265271300, 1265271360, 1265271420, 1265271480, 1265271540, 
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  1265271960, 1265272020, 1265272080, 1265272140, 1265272200, 1265272260, 
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  1265349720, 1265349780, 1265349840, 1265349900, 1265349960, 1265350020, 
  1265350080, 1265350140, 1265350200, 1265350260, 1265350320, 1265350380, 
  1265350440, 1265350500, 1265350560, 1265350620, 1265350680, 1265350740, 
  1265350800, 1265350860, 1265350920, 1265350980, 1265351040, 1265351100, 
  1265351160, 1265351220, 1265351280, 1265351340, 1265351400, 1265351460, 
  1265351520, 1265351580, 1265351640, 1265351700, 1265351760, 1265351820, 
  1265351880, 1265351940, 1265352000, 1265352060, 1265352120, 1265352180, 
  1265352240, 1265352300, 1265352360, 1265352420, 1265352480, 1265352540, 
  1265352600, 1265352660, 1265352720, 1265352780, 1265352840, 1265352900, 
  1265352960, 1265353020, 1265353080, 1265353140, 1265353200, 1265353260, 
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  1265357280, 1265357340, 1265357400, 1265357460, 1265357520, 1265357580, 
  1265357640, 1265357700, 1265357760, 1265357820, 1265357880, 1265357940, 
  1265358000, 1265358060, 1265358120, 1265358180, 1265358240, 1265358300, 
  1265358360, 1265358420, 1265358480, 1265358540, 1265358600, 1265358660, 
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  1265359440, 1265359500, 1265359560, 1265359620, 1265359680, 1265359740, 
  1265359800, 1265359860, 1265359920, 1265359980, 1265360040, 1265360100, 
  1265360160, 1265360220, 1265360280, 1265360340), tzone = "", class = c("POSIXct", 
  "POSIXt"))), .Names = c("all", "datetime"), row.names = c(NA, 
  540L), class = "data.frame")
  </code></pre>