为什么 Gnuplot 的点链接不好？

Question

我无法放置所有数据，因为：看起来您的帖子主要是代码；请添加更多详细信息。

所以你可以在这里找到我的数据：https://gitlab.com/v_alexandre/data/-/blob/master/data

脚本：

plot 'data' u 1:2 w l

正如你所看到的，我有两点联系在一起，但我不明白为什么？

你有什么想法吗？

Answer 1

在数据的第 6 行之后插入一个空行。这将断开两个岛屿的连接。

脚本：

### disconnect lines
reset session

$Data <<EOD
9.2710321280228 41.364959299521
9.265698545799 41.362164776515
9.2558829669799 41.368794222327
9.2602446048541 41.373651229899
9.273659440522 41.369221791575
9.2710321280228 41.364959299521

8.5734085639674 42.381404942274
8.5869206603959 42.378959456159
8.6000271534091 42.369259196001
8.6100160917347 42.373593854505
8.620173521868 42.372270719131
8.6408019259839 42.37343904341
8.6504088344609 42.362352538519
8.6596703887356 42.359406967225
8.6819749384239 42.358462008729
8.6841460127953 42.347988396554
8.7110680867563 42.347099989534
# ... not all data shown...
EOD

plot $Data u 1:2 w l
### end of script

结果：

补充：

仅供记录，一些更多的解释和代码可能对其类似情况下的其他人有用。 您的数据似乎描述了封闭区域的点，例如一些岛屿的坐标。由于某些（不幸的）原因，您的各个岛屿没有被空线分隔，这就是 gnuplot 一次性绘制它的原因。 gnuplot 应该如何知道在哪里分隔？ 你必须告诉gnuplot在哪里产生不连续性。但你怎么知道？

好吧，如果这些都是封闭区域，那么起点和终点应该是相同的。因此，您需要遍历数据，每次找到相同的数据点时，您都会在后面引入一个间隙（空行）。 当然，您不想手动执行此操作，例如如果您想到加拿大的岛屿或芬兰的湖泊。 当然，您可以使用外部工具执行此操作并将数据保存到另一个文件，但您也可以使用 gnuplot 执行此操作。然而，对于最终结果，仅“举笔”而不修改数据可能就足够了。使用 gnuplot，您可以发挥“技巧”并使该行透明，例如颜色

0xff123456

（根据方案

0xAARRGGBB

）无论哪种颜色只要以

0xff

开头即可，即完全透明。

总结：定义一个函数，每次特定坐标再次出现后将颜色设置为透明。也许有人甚至可以简化该功能。

数据：

SO65655925.dat

# x       y
-76.3499  18.1519
-76.7007  18.2572
-76.7933  18.3043
-76.9082  18.3904
-76.9594  18.4019
-77.0138  18.4029
-77.1396  18.4215
-77.2615  18.4574
-77.3542  18.4665
-77.4516  18.467
-77.8734  18.5222
-77.9269  18.5007
-77.9782  18.4678
-78.0945  18.4448
-78.2167  18.4481
-78.2524  18.4263
-78.326  18.3498
-78.3395  18.2872
-78.2941  18.2181
-78.0736  18.1912
-78.0445  18.1738
-77.963  18.0476
-77.8813  18.019
-77.8494  17.9875
-77.7682  17.8774
-77.6708  17.8597
-77.4639  17.8561
-77.3614  17.8337
-77.2799  17.7795
-77.205  17.7149
-77.1584  17.8451
-77.1195  17.8801
-77.0713  17.9013
-77.0359  17.8541
-76.9441  17.8488
-76.8962  17.9041
-76.8532  17.9737
-76.7948  17.9763
-76.7483  17.9649
-76.7743  17.9404
-76.6694  17.9276
-76.6254  17.901
-76.5246  17.8662
-76.4155  17.8682
-76.3015  17.8798
-76.2108  17.9135
-76.2328  17.9703
-76.3499  18.1519
-65.6288  18.3814
-65.7556  18.4016
-65.8788  18.4438
-66.0704  18.469
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-66.0985  18.4252
-66.1294  18.4449
-66.1531  18.4707
-66.1886  18.4758
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-67.0596  18.5222
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-66.5108  17.987
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-76.9281  21.459
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-81.1855  22.268
-81.1414  22.2069
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-81.0831  22.0979
-81.0356  22.0736
-80.9619  22.0529
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-80.4848  22.0872
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-68.6848  18.9048
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-73.6696  21.0822
-73.6678  21.0616
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-73.6812  20.9756
-73.661  20.9374
-73.9146  22.568
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-75.9486  23.6474
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-75.7542  23.49
-75.8075  23.5425
-75.9486  23.6474
-75.1306  23.2679
-75.1411  23.2046
-75.2044  23.1927
-75.2233  23.1653
-75.1321  23.1171
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-74.8469  22.8687
-74.8405  22.8943
-74.8456  22.9999
-74.9371  23.0881
-75.0642  23.1502
-75.1088  23.3328
-75.1753  23.4387
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-75.2413  23.4746
-75.1576  23.3364
-75.1306  23.2679
-77.8794  22.1275
-77.8425  22.149
-77.8891  22.2011
-77.8937  22.2146
-77.9696  22.2407
-77.9856  22.3021
-77.9992  22.2987
-78.0067  22.248
-78.0417  22.2013
-78.0119  22.1664
-77.9124  22.1247
-77.8794  22.1275
-82.6818  21.8211
-82.7146  21.8903
-82.7558  21.9095
-82.9912  21.9427
-83.0777  21.8335
-83.0825  21.7914
-82.9736  21.5923
-83.0072  21.5656
-83.0549  21.5494
-83.1129  21.5737
-83.1802  21.623
-83.1838  21.5935
-83.1415  21.5319
-83.0673  21.4694
-82.9596  21.4413
-82.8532  21.4439
-82.6548  21.5187
-82.5618  21.5717
-82.5678  21.6218
-82.6294  21.7669
-82.6818  21.8211
-79.3822  22.6813
-79.5792  22.8067
-79.6282  22.8052
-79.5979  22.7876
-79.5228  22.7111
-79.3479  22.6377
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-79.3822  22.6813
-81.2848  19.3625
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-81.391  19.3849
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-81.2848  19.3625
-62.7137  17.3533
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-62.8394  17.3653
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-62.8389  17.3393
-62.7755  17.3028
-62.702  17.286
-62.6565  17.2244
-62.6307  17.24
-62.6405  17.2623
-62.6758  17.2909
-62.7137  17.3533
-60.9337  14.6862
-60.9187  14.7354
-60.9271  14.7552
-60.9525  14.7562
-61.0271  14.8262
-61.1274  14.8753
-61.1808  14.8719
-61.2133  14.8486
-61.2197  14.8044
-61.1411  14.6524
-61.1043  14.6212
-61.0113  14.6019
-61.0903  14.5297
-61.0889  14.5096
-61.0637  14.4671
-60.8994  14.4738
-60.8621  14.4263
-60.8366  14.4374
-60.8263  14.4945
-60.87  14.6137
-60.8892  14.6445
-60.9337  14.6862
-62.1758  16.8096
-62.1914  16.8044
-62.223  16.7516
-62.2216  16.6995
-62.1542  16.6812
-62.1484  16.7403
-62.1758  16.8096
-63.16  18.1714
-63.0012  18.2218
-62.9796  18.2648
-63.026  18.2697
-63.1533  18.2003
-63.16  18.1714
-61.762  17.5487
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-61.7768  17.6905
-61.8199  17.6969
-61.8524  17.7141
-61.8662  17.7043
-61.8687  17.6854
-61.8438  17.5961
-61.762  17.5487
-61.25  16.0063
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-61.3107  15.8947
-61.2862  15.886
-61.2305  15.8899
-61.2034  15.9212
-61.2124  15.9599
-61.25  16.0063
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-61.7082  17.1051
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-72.9811  22.3692
-72.8892  22.3603
-72.7839  22.2906
-72.7473  22.3274
-72.7626  22.3444
-72.8308  22.3856
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-73.041  22.4291
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-73.1619  22.3807
-73.1102  22.3676
-72.9811  22.3692
-71.7218  21.7902
-71.6654  21.7517
-71.6614  21.7652
-71.6369  21.7875
-71.6684  21.8334
-71.8062  21.8521
-71.8477  21.8435
-71.8304  21.7906
-71.7218  21.7902
-72.9161  21.5067
-72.9948  21.5616
-73.0627  21.5153
-73.0493  21.4576
-72.9161  21.5067
-71.9555  21.8644
-71.8975  21.8299
-71.8799  21.8404
-71.8996  21.8625
-71.9315  21.9519
-72.0106  21.9504
-72.019  21.9183
-71.9845  21.8934
-71.9638  21.892
-71.9555  21.8644
-72.1907  21.7698
-72.1815  21.78
-72.1443  21.7927
-72.1498  21.8045
-72.2187  21.7963
-72.3328  21.8514
-72.3424  21.7953
-72.3354  21.758
-72.3009  21.7552
-72.1907  21.7698
-72.8515  20.0937
-72.9067  20.0858
-72.9604  20.0623
-72.8993  20.0314
-72.8784  20.0274
-72.8442  20.0354
-72.7398  20.0034
-72.6389  19.9858
-72.6235  20.0142
-72.6641  20.0375
-72.791  20.0919
-72.8515  20.0937

脚本：（适用于 gnuplot>=5.0.0，2015 年 1 月）

### autoseparation of data describing closed areas 
reset session

FILE = "SO65655925.dat"

# function to set color to transparent when coordinate appears again
myColor(colX,colY,color) = \
    ($0==0 ? (x2=y2=NaN, c=0, x0=column(colX), y0=column(colY)) : 0, \
     x1=x2, x2=column(colX), y1=y2, y2=column(colY), \
     x1==x0 && y1==y0 ? c=c+1 : 0, c==2 ? (c=0,x0=x2,y0=y2) : 0, \
     c==0 && $0!=0 ? 0xff123456 : color )

set multiplot layout 2,1
    plot FILE u 1:2 w l lc "black" ti "Data as is"

    plot FILE u 1:2:(myColor(1,2,0xff0000)) w l lc rgb var ti 'Data with "autoseparation"'
unset multiplot
### end of script

结果：