过滤指定网格框上的TC轨迹(纬度点) [英] Filter TC tracks (lat-lon points) over a specified gridbox

问题描述

我正在使用R过滤通过格网盒的热带气旋轨道.我有一个包含轨道的csv文件，并将它们转换为shapefile.

I am using R to filter Tropical cyclone tracks passing over a grid box. I have a csv file containing the tracks and convert them to a shapefile.

我只想过滤经过指定网格框(5N到25N和115E到135 E)的具有相同标识符(下面的示例数据中的"SN"列)的点.下面是我正在使用的代码和数据链接.

I wanted to filter only the points with the same identifier (the "SN" column in the sample data below) that passed over a specified grid box (5N to 25N and 115E to 135 E). Below is the code that I am using and the link to the data.

jtwc   <- read.csv("1979-1993_TC.csv",header=T,sep=",")

latmin <-5.00
latmax <- 25.00
lonmin <- 115.00
lonmax <- 135.00

jtwc.unique <- unique(jtwc[jtwc$Lat >= latmin & jtwc$Lat <= latmax & jtwc$Lon >= lonmin & jtwc$Lon <= lonmax,c(1,2)])
jtwc.filter <- merge(jtwc,jtwc.unique,all.x = F,all.y = T, sort = F)
jtwc.filter$Lon <- ifelse(jtwc.filter$Lon < 0, jtwc.filter$Lon + 360, jtwc.filter$Lon)
jtwc.filter <- jtwc.filter[with(jtwc.filter,order(Year,Month,Day,Hour,CY)),]

write.table(jtwc.filter,file = "test2_jul_par_1979-1993.csv", sep = ",", row.names = F)

问题:

此代码无法正常工作.运行脚本时，仍然可以看到框外的曲目.

This code does not work properly. When I ran the script, I still see tracks outside the box.

有人可以提出任何改进建议的方法吗?

Can anyone suggest any way to improve this?

我将不胜感激.

推荐答案

这是一种使用data.table进行数据处理，然后使用googleway在Google地图上绘制轨迹的方法

Here's an approach that uses data.table to do the data manipulation, then uses googleway to plot the tracks on google maps

library(googleway)
library(data.table) ## because I like working with data.table to do data manipulation

jtwc <- read.csv("~/Downloads/1979-1993_TC.csv")
setDT(jtwc)  ## set as data.table

latmin <-5.00
latmax <- 25.00
lonmin <- 115.00
lonmax <- 135.00

df_bounds <- data.frame(north = latmax, south = latmin, west = lonmin, east = lonmax)

## apply a logical column whether the point is in the box
jtwc[, inBounds := Lat >= latmin & Lat <= latmax & Lon >= lonmin & Lon <= lonmax]


## create a column that identifies if the SN at some point passes through the box
jtwc[SN %in% jtwc[inBounds == TRUE, unique(SN)], passesThroughBox := T ]
jtwc[is.na(passesThroughBox), passesThroughBox := F]

## adding a colour for plotting
jtwc[, colour := ifelse(passesThroughBox, "#4286F4", "#F44141") ]

## you need a google maps API key to plot on Google Maps
map_key <- 'your_api_key'

google_map(key = map_key) %>%
    add_polylines(data = jtwc, lat = "Lat", lon = "Lon", id = "SN", stroke_colour = 'colour',
                                mouse_over_group = 'passesThroughBox') %>%
    add_rectangles(data = df_bounds, north = 'north', south = 'south', west = 'west', east = 'east',
                                 fill_opacity = 0.1)

然后，当鼠标悬停在行上方时，您会看到通过的行

Then when hovering over the lines, you can see the ones that pass through

这篇关于过滤指定网格框上的TC轨迹(纬度点)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！