这似乎相对简单，并且可能使用 scale_x_datetime 或 scale_x_discrete 是可行的。
我有一个时间增量列，例如秒表：
[1] 0:00:01 0:00:02 0:00:03 0:00:04 0:00:05 0:00:06
1800 Levels: 0:00:01 0:00:02 0:00:03 0:00:04 0:00:05 0:00:06 0:00:07 ... 0:30:00
使用 ggplot 如何将 x 轴标签设置为 30 秒间隔？
可重现的数据：
structure(list(`somedata$Time` = structure(1:4, .Label = c("0:00:01",
"0:00:02", "0:00:03", "0:00:04", "0:00:05", "0:00:06", "0:00:07",
"0:00:08", "0:00:09", "0:00:10", "0:00:11", "0:00:12", "0:00:13",
"0:00:14", "0:00:15", "0:00:16", "0:00:17", "0:00:18", "0:00:19",
"0:00:20", "0:00:21", "0:00:22", "0:00:23", "0:00:24", "0:00:25",
"0:00:26", "0:00:27", "0:00:28", "0:00:29", "0:00:30", "0:00:31",
"0:00:32", "0:00:33", "0:00:34", "0:00:35", "0:00:36", "0:00:37",
"0:00:38", "0:00:39", "0:00:40", "0:00:41", "0:00:42", "0:00:43",
"0:00:44", "0:00:45", "0:00:46", "0:00:47", "0:00:48", "0:00:49",
"0:00:50", "0:00:51", "0:00:52", "0:00:53", "0:00:54", "0:00:55",
"0:00:56", "0:00:57", "0:00:58", "0:00:59", "0:01:00", "0:01:01",
"0:01:02", "0:01:03", "0:01:04", "0:01:05", "0:01:06", "0:01:07",
"0:01:08", "0:01:09", "0:01:10", "0:01:11", "0:01:12", "0:01:13",
"0:01:14", "0:01:15", "0:01:16", "0:01:17", "0:01:18", "0:01:19",
"0:01:20", "0:01:21", "0:01:22", "0:01:23", "0:01:24", "0:01:25",
"0:01:26", "0:01:27", "0:01:28", "0:01:29", "0:01:30", "0:01:31",
"0:01:32", "0:01:33", "0:01:34", "0:01:35", "0:01:36", "0:01:37",
"0:01:38", "0:01:39", "0:01:40", "0:01:41", "0:01:42", "0:01:43",
"0:01:44", "0:01:45", "0:01:46", "0:01:47", "0:01:48", "0:01:49",
"0:01:50", "0:01:51", "0:01:52", "0:01:53", "0:01:54", "0:01:55",
"0:01:56", "0:01:57", "0:01:58", "0:01:59", "0:02:00", "0:02:01",
"0:02:02", "0:02:03", "0:02:04", "0:02:05", "0:02:06", "0:02:07",
"0:02:08", "0:02:09", "0:02:10", "0:02:11", "0:02:12", "0:02:13",
"0:02:14", "0:02:15", "0:02:16", "0:02:17", "0:02:18", "0:02:19",
"0:02:20", "0:02:21", "0:02:22", "0:02:23", "0:02:24", "0:02:25",
"0:02:26", "0:02:27", "0:02:28", "0:02:29", "0:02:30", "0:02:31",
"0:02:32", "0:02:33", "0:02:34", "0:02:35", "0:02:36", "0:02:37",
"0:02:38", "0:02:39", "0:02:40", "0:02:41", "0:02:42", "0:02:43",
"0:02:44", "0:02:45", "0:02:46", "0:02:47", "0:02:48", "0:02:49",
"0:02:50", "0:02:51", "0:02:52", "0:02:53", "0:02:54", "0:02:55",
"0:02:56", "0:02:57", "0:02:58", "0:02:59", "0:03:00", "0:03:01",
"0:03:02", "0:03:03", "0:03:04", "0:03:05", "0:03:06", "0:03:07",
"0:03:08", "0:03:09", "0:03:10", "0:03:11", "0:03:12", "0:03:13",
"0:03:14", "0:03:15", "0:03:16", "0:03:17", "0:03:18", "0:03:19",
"0:03:20", "0:03:21", "0:03:22", "0:03:23", "0:03:24", "0:03:25",
"0:03:26", "0:03:27", "0:03:28", "0:03:29", "0:03:30", "0:03:31",
"0:03:32", "0:03:33", "0:03:34", "0:03:35", "0:03:36", "0:03:37",
"0:03:38", "0:03:39", "0:03:40", "0:03:41", "0:03:42", "0:03:43",
"0:03:44", "0:03:45", "0:03:46", "0:03:47", "0:03:48", "0:03:49",
"0:03:50", "0:03:51", "0:03:52", "0:03:53", "0:03:54", "0:03:55",
"0:03:56", "0:03:57", "0:03:58", "0:03:59", "0:04:00", "0:04:01",
"0:04:02", "0:04:03", "0:04:04", "0:04:05", "0:04:06", "0:04:07",
"0:04:08", "0:04:09", "0:04:10", "0:04:11", "0:04:12", "0:04:13",
"0:04:14", "0:04:15", "0:04:16", "0:04:17", "0:04:18", "0:04:19",
"0:04:20", "0:04:21", "0:04:22", "0:04:23", "0:04:24", "0:04:25",
"0:04:26", "0:04:27", "0:04:28", "0:04:29", "0:04:30", "0:04:31",
"0:04:32", "0:04:33", "0:04:34", "0:04:35", "0:04:36", "0:04:37",
"0:04:38", "0:04:39", "0:04:40", "0:04:41", "0:04:42", "0:04:43",
"0:04:44", "0:04:45", "0:04:46", "0:04:47", "0:04:48", "0:04:49",
"0:04:50", "0:04:51", "0:04:52", "0:04:53", "0:04:54", "0:04:55",
"0:04:56", "0:04:57", "0:04:58", "0:04:59", "0:05:00", "0:05:01",
"0:05:02", "0:05:03", "0:05:04", "0:05:05", "0:05:06", "0:05:07",
"0:05:08", "0:05:09", "0:05:10", "0:05:11", "0:05:12", "0:05:13",
"0:05:14", "0:05:15", "0:05:16", "0:05:17", "0:05:18", "0:05:19",
"0:05:20", "0:05:21", "0:05:22", "0:05:23", "0:05:24", "0:05:25",
"0:05:26", "0:05:27", "0:05:28", "0:05:29", "0:05:30", "0:05:31",
"0:05:32", "0:05:33", "0:05:34", "0:05:35", "0:05:36", "0:05:37",
"0:05:38", "0:05:39", "0:05:40", "0:05:41", "0:05:42", "0:05:43",
"0:05:44", "0:05:45", "0:05:46", "0:05:47", "0:05:48", "0:05:49",
"0:05:50", "0:05:51", "0:05:52", "0:05:53", "0:05:54", "0:05:55",
"0:05:56", "0:05:57", "0:05:58", "0:05:59", "0:06:00", "0:06:01",
"0:06:02", "0:06:03", "0:06:04", "0:06:05", "0:06:06", "0:06:07",
"0:06:08", "0:06:09", "0:06:10", "0:06:11", "0:06:12", "0:06:13",
"0:06:14", "0:06:15", "0:06:16", "0:06:17", "0:06:18", "0:06:19",
"0:06:20", "0:06:21", "0:06:22", "0:06:23", "0:06:24", "0:06:25",
"0:06:26", "0:06:27", "0:06:28", "0:06:29", "0:06:30", "0:06:31",
"0:06:32", "0:06:33", "0:06:34", "0:06:35", "0:06:36", "0:06:37",
"0:06:38", "0:06:39", "0:06:40", "0:06:41", "0:06:42", "0:06:43",
"0:06:44", "0:06:45", "0:06:46", "0:06:47", "0:06:48", "0:06:49",
"0:06:50", "0:06:51", "0:06:52", "0:06:53", "0:06:54", "0:06:55",
"0:06:56", "0:06:57", "0:06:58", "0:06:59", "0:07:00", "0:07:01",
"0:07:02", "0:07:03", "0:07:04", "0:07:05", "0:07:06", "0:07:07",
"0:07:08", "0:07:09", "0:07:10", "0:07:11", "0:07:12", "0:07:13",
"0:07:14", "0:07:15", "0:07:16", "0:07:17", "0:07:18", "0:07:19",
"0:07:20", "0:07:21", "0:07:22", "0:07:23", "0:07:24", "0:07:25",
"0:07:26", "0:07:27", "0:07:28", "0:07:29", "0:07:30", "0:07:31",
"0:07:32", "0:07:33", "0:07:34", "0:07:35", "0:07:36", "0:07:37",
"0:07:38", "0:07:39", "0:07:40", "0:07:41", "0:07:42", "0:07:43",
"0:07:44", "0:07:45", "0:07:46", "0:07:47", "0:07:48", "0:07:49",
"0:07:50", "0:07:51", "0:07:52", "0:07:53", "0:07:54", "0:07:55",
"0:07:56", "0:07:57", "0:07:58", "0:07:59", "0:08:00", "0:08:01",
"0:08:02", "0:08:03", "0:08:04", "0:08:05", "0:08:06", "0:08:07",
"0:08:08", "0:08:09", "0:08:10", "0:08:11", "0:08:12", "0:08:13",
"0:08:14", "0:08:15", "0:08:16", "0:08:17", "0:08:18", "0:08:19",
"0:08:20", "0:08:21", "0:08:22", "0:08:23", "0:08:24", "0:08:25",
"0:08:26", "0:08:27", "0:08:28", "0:08:29", "0:08:30", "0:08:31",
"0:08:32", "0:08:33", "0:08:34", "0:08:35", "0:08:36", "0:08:37",
"0:08:38", "0:08:39", "0:08:40", "0:08:41", "0:08:42", "0:08:43",
"0:08:44", "0:08:45", "0:08:46", "0:08:47", "0:08:48", "0:08:49",
"0:08:50", "0:08:51", "0:08:52", "0:08:53", "0:08:54", "0:08:55",
"0:08:56", "0:08:57", "0:08:58", "0:08:59", "0:09:00", "0:09:01",
"0:09:02", "0:09:03", "0:09:04", "0:09:05", "0:09:06", "0:09:07",
"0:09:08", "0:09:09", "0:09:10", "0:09:11", "0:09:12", "0:09:13",
"0:09:14", "0:09:15", "0:09:16", "0:09:17", "0:09:18", "0:09:19",
"0:09:20", "0:09:21", "0:09:22", "0:09:23", "0:09:24", "0:09:25",
"0:09:26", "0:09:27", "0:09:28", "0:09:29", "0:09:30", "0:09:31",
"0:09:32", "0:09:33", "0:09:34", "0:09:35", "0:09:36", "0:09:37",
"0:09:38", "0:09:39", "0:09:40", "0:09:41", "0:09:42", "0:09:43",
"0:09:44", "0:09:45", "0:09:46", "0:09:47", "0:09:48", "0:09:49",
"0:09:50", "0:09:51", "0:09:52", "0:09:53", "0:09:54", "0:09:55",
"0:09:56", "0:09:57", "0:09:58", "0:09:59", "0:10:00", "0:10:01",
"0:10:02", "0:10:03", "0:10:04", "0:10:05", "0:10:06", "0:10:07",
"0:10:08", "0:10:09", "0:10:10", "0:10:11", "0:10:12", "0:10:13",
"0:10:14", "0:10:15", "0:10:16", "0:10:17", "0:10:18", "0:10:19",
"0:10:20", "0:10:21", "0:10:22", "0:10:23", "0:10:24", "0:10:25",
"0:10:26", "0:10:27", "0:10:28", "0:10:29", "0:10:30", "0:10:31",
"0:10:32", "0:10:33", "0:10:34", "0:10:35", "0:10:36", "0:10:37",
"0:10:38", "0:10:39", "0:10:40", "0:10:41", "0:10:42", "0:10:43",
"0:10:44", "0:10:45", "0:10:46", "0:10:47", "0:10:48", "0:10:49",
"0:10:50", "0:10:51", "0:10:52", "0:10:53", "0:10:54", "0:10:55",
"0:10:56", "0:10:57", "0:10:58", "0:10:59", "0:11:00", "0:11:01",
"0:11:02", "0:11:03", "0:11:04", "0:11:05", "0:11:06", "0:11:07",
"0:11:08", "0:11:09", "0:11:10", "0:11:11", "0:11:12", "0:11:13",
"0:11:14", "0:11:15", "0:11:16", "0:11:17", "0:11:18", "0:11:19",
"0:11:20", "0:11:21", "0:11:22", "0:11:23", "0:11:24", "0:11:25",
"0:11:26", "0:11:27", "0:11:28", "0:11:29", "0:11:30", "0:11:31",
"0:11:32", "0:11:33", "0:11:34", "0:11:35", "0:11:36", "0:11:37",
"0:11:38", "0:11:39", "0:11:40", "0:11:41", "0:11:42", "0:11:43",
"0:11:44", "0:11:45", "0:11:46", "0:11:47", "0:11:48", "0:11:49",
"0:11:50", "0:11:51", "0:11:52", "0:11:53", "0:11:54", "0:11:55",
"0:11:56", "0:11:57", "0:11:58", "0:11:59", "0:12:00", "0:12:01",
"0:12:02", "0:12:03", "0:12:04", "0:12:05", "0:12:06", "0:12:07",
"0:12:08", "0:12:09", "0:12:10", "0:12:11", "0:12:12", "0:12:13",
"0:12:14", "0:12:15", "0:12:16", "0:12:17", "0:12:18", "0:12:19",
"0:12:20", "0:12:21", "0:12:22", "0:12:23", "0:12:24", "0:12:25",
"0:12:26", "0:12:27", "0:12:28", "0:12:29", "0:12:30", "0:12:31",
"0:12:32", "0:12:33", "0:12:34", "0:12:35", "0:12:36", "0:12:37",
"0:12:38", "0:12:39", "0:12:40", "0:12:41", "0:12:42", "0:12:43",
"0:12:44", "0:12:45", "0:12:46", "0:12:47", "0:12:48", "0:12:49",
"0:12:50", "0:12:51", "0:12:52", "0:12:53", "0:12:54", "0:12:55",
"0:12:56", "0:12:57", "0:12:58", "0:12:59", "0:13:00", "0:13:01",
"0:13:02", "0:13:03", "0:13:04", "0:13:05", "0:13:06", "0:13:07",
"0:13:08", "0:13:09", "0:13:10", "0:13:11", "0:13:12", "0:13:13",
"0:13:14", "0:13:15", "0:13:16", "0:13:17", "0:13:18", "0:13:19",
"0:13:20", "0:13:21", "0:13:22", "0:13:23", "0:13:24", "0:13:25",
"0:13:26", "0:13:27", "0:13:28", "0:13:29", "0:13:30", "0:13:31",
"0:13:32", "0:13:33", "0:13:34", "0:13:35", "0:13:36", "0:13:37",
"0:13:38", "0:13:39", "0:13:40", "0:13:41", "0:13:42", "0:13:43",
"0:13:44", "0:13:45", "0:13:46", "0:13:47", "0:13:48", "0:13:49",
"0:13:50", "0:13:51", "0:13:52", "0:13:53", "0:13:54", "0:13:55",
"0:13:56", "0:13:57", "0:13:58", "0:13:59", "0:14:00", "0:14:01",
"0:14:02", "0:14:03", "0:14:04", "0:14:05", "0:14:06", "0:14:07",
"0:14:08", "0:14:09", "0:14:10", "0:14:11", "0:14:12", "0:14:13",
"0:14:14", "0:14:15", "0:14:16", "0:14:17", "0:14:18", "0:14:19",
"0:14:20", "0:14:21", "0:14:22", "0:14:23", "0:14:24", "0:14:25",
"0:14:26", "0:14:27", "0:14:28", "0:14:29", "0:14:30", "0:14:31",
"0:14:32", "0:14:33", "0:14:34", "0:14:35", "0:14:36", "0:14:37",
"0:14:38", "0:14:39", "0:14:40", "0:14:41", "0:14:42", "0:14:43",
"0:14:44", "0:14:45", "0:14:46", "0:14:47", "0:14:48", "0:14:49",
"0:14:50", "0:14:51", "0:14:52", "0:14:53", "0:14:54", "0:14:55",
"0:14:56", "0:14:57", "0:14:58", "0:14:59", "0:15:00", "0:15:01",
"0:15:02", "0:15:03", "0:15:04", "0:15:05", "0:15:06", "0:15:07",
"0:15:08", "0:15:09", "0:15:10", "0:15:11", "0:15:12", "0:15:13",
"0:15:14", "0:15:15", "0:15:16", "0:15:17", "0:15:18", "0:15:19",
"0:15:20", "0:15:21", "0:15:22", "0:15:23", "0:15:24", "0:15:25",
"0:15:26", "0:15:27", "0:15:28", "0:15:29", "0:15:30", "0:15:31",
"0:15:32", "0:15:33", "0:15:34", "0:15:35", "0:15:36", "0:15:37",
"0:15:38", "0:15:39", "0:15:40", "0:15:41", "0:15:42", "0:15:43",
"0:15:44", "0:15:45", "0:15:46", "0:15:47", "0:15:48", "0:15:49",
"0:15:50", "0:15:51", "0:15:52", "0:15:53", "0:15:54", "0:15:55",
"0:15:56", "0:15:57", "0:15:58", "0:15:59", "0:16:00", "0:16:01",
"0:16:02", "0:16:03", "0:16:04", "0:16:05", "0:16:06", "0:16:07",
"0:16:08", "0:16:09", "0:16:10", "0:16:11", "0:16:12", "0:16:13",
"0:16:14", "0:16:15", "0:16:16", "0:16:17", "0:16:18", "0:16:19",
"0:16:20", "0:16:21", "0:16:22", "0:16:23", "0:16:24", "0:16:25",
"0:16:26", "0:16:27", "0:16:28", "0:16:29", "0:16:30", "0:16:31",
"0:16:32", "0:16:33", "0:16:34", "0:16:35", "0:16:36", "0:16:37",
"0:16:38", "0:16:39", "0:16:40", "0:16:41", "0:16:42", "0:16:43",
"0:16:44", "0:16:45", "0:16:46", "0:16:47", "0:16:48", "0:16:49",
"0:16:50", "0:16:51", "0:16:52", "0:16:53", "0:16:54", "0:16:55",
"0:16:56", "0:16:57", "0:16:58", "0:16:59", "0:17:00", "0:17:01",
"0:17:02", "0:17:03", "0:17:04", "0:17:05", "0:17:06", "0:17:07",
"0:17:08", "0:17:09", "0:17:10", "0:17:11", "0:17:12", "0:17:13",
"0:17:14", "0:17:15", "0:17:16", "0:17:17", "0:17:18", "0:17:19",
"0:17:20", "0:17:21", "0:17:22", "0:17:23", "0:17:24", "0:17:25",
"0:17:26", "0:17:27", "0:17:28", "0:17:29", "0:17:30", "0:17:31",
"0:17:32", "0:17:33", "0:17:34", "0:17:35", "0:17:36", "0:17:37",
"0:17:38", "0:17:39", "0:17:40", "0:17:41", "0:17:42", "0:17:43",
"0:17:44", "0:17:45", "0:17:46", "0:17:47", "0:17:48", "0:17:49",
"0:17:50", "0:17:51", "0:17:52", "0:17:53", "0:17:54", "0:17:55",
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