Convert Each Multilinestring to One Linestring Only
In This Shapefile, the Geometry Column Is Linestring Apart from 4 Stream Reaches (8168547, 8171738, 8170616,8169920) That Are Multilinestring. I Need to...
In this shapefile, the geometry column is linestring apart from 4 stream reaches (8168547, 8171738, 8170616 ,8169920) that are multilinestring.
I need to convert each multilinestring to one linestring only .
I have tried many things but none worked. For example, I tried st_cast in sf package in R. However, it increased the number of the rows (it converts each multilinestring to several linestrings).
How can I convert each multilinestring to one linestring only?
2 Answers
in geopandas, this can be done with explode:
import geopandas as gpd
gdf = gpd.read_file(filepath)
exploded = gdf.explode()
The {sf} way of converting multilinestrings to linestrings would be, as you mention, via sf::st_cast().
But there is a problem with your data - some of the streams are not possible to make into simple linestrings. A linestring must have a single start and a single end point - this is simply not possible for some of your rchids. As a result some of your objects end up being duplicated.
As this is a general failure - and not a R specific one - I would expect the comment to be valid also for geopandas, although I have not ran the code to verify.
I suggest first casting your object to linestrings, then identifying duplicites and filtering them out.
library(sf)
library(dplyr)
streams <- st_read("tukituki_rivStrah3.shp") %>%
select(-length) %>% # filtering out, as length is a derived metric
st_cast("LINESTRING")
duplicities <- streams %>%
st_drop_geometry() %>%
group_by(rchid) %>%
tally %>%
filter(n > 1) %>%
pull(rchid)
# this will not do...
mapview::mapview(streams[streams$rchid == duplicities[2],])
clean_streams <- streams %>%
filter(!rchid %in% duplicities)
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