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I am new to spatstat package and I am trying to make a point patten map with a shape file and some case points. I was able to plot the shape file plot but I just don't know how to make the points on the map plot through the spastat object even I tried points() function or plot() function. What am I missing?

pacman::p_load(sf, sp, spatstat)

# shape file
manchester_ward <- st_read("https://raw.githubusercontent.com/RUMgroup/Spatial-data-in-R/master/rumgroup/data/wards.geojson")
Fallowfield <- manchester_ward %>% dplyr::filter(wd16nm == "Fallowfield")
Fallowfield_pp <- as.owin(Fallowfield)
plot(Fallowfield_pp)

# points
crime <- structure(list(crime_type = c("Burglary", "Burglary", "Burglary", 
"Burglary", "Burglary", "Burglary"), geometry = structure(list(
    structure(c(-2.242511, 53.44558), class = c("XY", "POINT", 
    "sfg")), structure(c(-2.237017, 53.445735), class = c("XY", 
    "POINT", "sfg")), structure(c(-2.2334, 53.442408), class = c("XY", 
    "POINT", "sfg")), structure(c(-2.242048, 53.448871), class = c("XY", 
    "POINT", "sfg")), structure(c(-2.242048, 53.448871), class = c("XY", 
    "POINT", "sfg")), structure(c(-2.243242, 53.444339), class = c("XY", 
    "POINT", "sfg"))), class = c("sfc_POINT", "sfc"), precision = 0, bbox = structure(c(xmin = -2.243242, 
ymin = 53.442408, xmax = -2.2334, ymax = 53.448871), class = "bbox"), crs = structure(list(
    input = "EPSG:4326", wkt = "GEOGCRS[\"WGS 84\",\n    DATUM[\"World Geodetic System 1984\",\n        ELLIPSOID[\"WGS 84\",6378137,298.257223563,\n            LENGTHUNIT[\"metre\",1]]],\n    PRIMEM[\"Greenwich\",0,\n        ANGLEUNIT[\"degree\",0.0174532925199433]],\n    CS[ellipsoidal,2],\n        AXIS[\"geodetic latitude (Lat)\",north,\n            ORDER[1],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n        AXIS[\"geodetic longitude (Lon)\",east,\n            ORDER[2],\n            ANGLEUNIT[\"degree\",0.0174532925199433]],\n    USAGE[\n        SCOPE[\"Horizontal component of 3D system.\"],\n        AREA[\"World.\"],\n        BBOX[-90,-180,90,180]],\n    ID[\"EPSG\",4326]]"), class = "crs"), n_empty = 0L)), sf_column = "geometry", agr = structure(c(crime_type = 1L), .Label = c("constant", 
"aggregate", "identity"), class = "factor"), row.names = c(NA, 
6L), class = c("sf", "data.table", "data.frame"))

crime_pt <- matrix(unlist(crime$geometry), ncol = 2, byrow = T)
k1 <- ppp(x = crime_pt[,1], y = crime_pt[,2],
          window = Fallowfield_pp, check = T)
plot(k1)

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  • What's windows in the ppp call at the end? Also you should never load tidyverse since it pulls in so much - all you are using from that is filter which you could get better with dplyr::filter (since then it couldn't clash with base::filter). – Spacedman Mar 19 at 12:29
  • Thanks @Spacedman. The windows was supposed to be "Fallowfield_pp". I edited out the tidyverse and others. I got a warning message: Warning message: In plot.ppp(k1) : 6 illegal points also plotted and an almost blank page in the plot panel. – Gnin Mar 19 at 12:35
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Different coordinate systems. Fallowfield is this:

> Fallowfield_pp 
window: polygonal boundary
enclosing rectangle: [382951.5, 385869.8] x [393616.3, 394988.8] units

and your crime is:

> crime
Simple feature collection with 6 features and 1 field
Attribute-geometry relationship: 1 constant, 0 aggregate, 0 identity
geometry type:  POINT
dimension:      XY
bbox:           xmin: -2.243242 ymin: 53.44241 xmax: -2.2334 ymax: 53.44887
geographic CRS: WGS 84
  crime_type                   geometry
1   Burglary POINT (-2.242511 53.44558)
2   Burglary POINT (-2.237017 53.44573)
3   Burglary   POINT (-2.2334 53.44241)
4   Burglary POINT (-2.242048 53.44887)

notice the very different coordinate numbers. Fallowfield is British National Grid and crime is WGS84 lat-long.

Let's convert the crime data to the same coordinate system as the Fallowfield boundary:

 crime = st_transform(crime, st_crs(Fallowfield))

and then go through your ppp construction again and you get:

enter image description here

with a duplicate point warning, because point pattern statistics is based on points being generated on the continuum, but that's not important right now I guess...

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  • Thanks and I didn't know they're in different systems! And I didn't recognise you earlier - big fan of your spatial course! I guess I should have given you more points! – Gnin Mar 19 at 13:15

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