Exercise in grImport

红太狼 2022-09-25 08:22 112阅读 0赞

Last week I used grImport for the first time. I decided to try perform another exercise using it. The task was to add voivodeship division of Poland.

Standard R maps do not contain such a division. I have found it on r-forge in package  [mapoland][] based on ESRI shape files, but I wanted to import such a map from SVG file which can be found on[Wikipedia][]. As last time SVG file has to be converted do PS first. Here is a comparison of both maps showing that the import worked quite well.

[![woj.png_zoom_2_resize_320_2C304][]][woj.png_zoom_2_resize_320_2C304 1]

And this is the code I have used:

library **(**grImport **)**

PostScriptTrace **(** “Wojewodztwa.ps” **)**

voiv  **<-** readPicture **(** “Wojewodztwa.ps.xml” **)**

broken.voiv  **<-** explodePaths **(**voiv **)**

\#extracting voivodeship ‘PictureStrokes’

xpath  **<-** ypath  **<-**  list **()**

sel  **<-**  c **(** 2, 4, 6, 8, 20, 22, 24, 28, 30, 32, 34, 36, 38, 41, 44, 46 **)**

**for (**i  **in**  seq **(**along  **= **sel **)) \{**

xpath **\[\[**i **\]\] <-** broken.voiv **\[\[**sel **\[**i **\]\]\]**@paths **$**path@x

ypath **\[\[**i **\]\] <-** broken.voiv **\[\[**sel **\[**i **\]\]\]**@paths **$**path@y

**\}**

\#adding Wolin island to zachodniopomorskie

xpath **\[\[** 2 **\]\] <-**  c **(**broken.voiv **\[** 10 **\]**@paths **$**path@x **\[** c **(** 39 **:** 1, 95 **:** 40 **)\]**,

xpath **\[\[** 2 **\]\])**

ypath **\[\[** 2 **\]\] <-**  c **(**broken.voiv **\[** 10 **\]**@paths **$**path@y **\[** c **(** 39 **:** 1, 95 **:** 40 **)\]**,

ypath **\[\[** 2 **\]\])**

library **(**mapoland **)**

pl  **<-** getShape **(** “voiv” **)**

\#functions rescaling paths to mapoland map size

transx  **<- function(**x **) \{**

old  **<-**  c **(** min **(** sapply **(**xpath, min **))**, max **(** sapply **(**xpath, max **)))**

new  **<-** pl@bbox **\[** 1, **\]**

**((**x  **–** old **\[** 1 **\]) / (**old **\[** 2 **\] – **old **\[** 1 **\])) \* (**new **\[** 2 **\] –**new **\[** 1 **\])**

**    \+** new **\[** 1 **\]**

**\}**

transy  **<- function(**y **) \{**

old  **<-**  c **(** min **(** sapply **(**ypath,  min **))**,  max **(** sapply **(**ypath, max **)))**

new  **<-** pl@bbox **\[** 2, **\]**

**((**y  **–** old **\[** 1 **\]) / (**old **\[** 2 **\] – **old **\[** 1 **\])) \* (**new **\[** 2 **\] –**new **\[** 1 **\])**

**    \+** new **\[** 1 **\]**

**\}**

plot **(**pl, lwd  **=**  4 **)**

**for (**i  **in**  seq **(**along  **= **sel **)) \{**

lines **(**transx **(**xpath **\[\[**i **\]\])**, transy **(**ypath **\[\[**i **\]\])**, col  **=** “red” **)**

**\}**

[mapoland]: http://mapoland.r-forge.r-project.org/
[Wikipedia]: http://upload.wikimedia.org/wikipedia/commons/4/4e/Wojewodztwa.svg
[woj.png_zoom_2_resize_320_2C304]: https://i1.wp.com/1.bp.blogspot.com/-1jASxKhAJEE/TxARHoBpIaI/AAAAAAAAACM/qOma9C_EUZA/s320/woj.png?zoom=2&resize=320%2C304
[woj.png_zoom_2_resize_320_2C304 1]: https://i0.wp.com/1.bp.blogspot.com/-1jASxKhAJEE/TxARHoBpIaI/AAAAAAAAACM/qOma9C_EUZA/s1600/woj.png