Loop chapter with map

Question

I need to create a document to show the interventions done in different neighborhoods, I´d like to do it on a loop as the maps are all the same, except with different shapefiles that are named the same (i.e., streets_zone1, streets_zone2, lights_zone1, lights_zone2, ...)

I´ve tried several things but I end up copy pasting the code multiple times

This is the code I came up with in markdown

### Zone1

```{r MapZone1, echo=FALSE, message=FALSE, warning=FALSE}
lights_zone1 <- st_intersection(lights.shp, zone1.shp)
streets_zone1 <- st_intersection(streets.shp, zone1.shp)

tmap_mode("view")
tm_basemap(leaflet::providers$OpenStreetMap) +
  tm_shape(Zone1.shp) +
  tm_dots(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080") +
  tm_shape(streets_zone1) +
  tm_fill(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080") +
  tm_shape(lights_zone1) +
  tm_fill(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080")

### Zone2

```{r MapZone2, echo=FALSE, message=FALSE, warning=FALSE}
lights_Zone2 <- st_intersection(lights.shp, Zone2.shp)
streets_Zone2 <- st_intersection(streets.shp, Zone2.shp)

tmap_mode("view")
tm_basemap(leaflet::providers$OpenStreetMap) +
  tm_shape(Zone2.shp) +
  tm_dots(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080") +
  tm_shape(streets_Zone2) +
  tm_fill(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080") +
  tm_shape(lights_Zone2) +
  tm_fill(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080")

and so on...

another thing I tried was filtering instead of the st_intersection but it would be the same

eventually y came up with the code

```{r echo=FALSE, message=FALSE, warning=FALSE, results='asis'}
anexos <- as.list(Zonas.shp$NOMBRE)
for (k in 1:length(anexos)) {
  zonas <- paste0("Zona_", anexos[k])
  wd <- anexos[k]
  assign(Zonas, subset(Zonas.shp, Zonas.shp$NOMBRE == wd))
  ligths <- paste0("ligths_", anexos[k])
  assign(ligths, raster::intersect(paste0("ligths_", wd), ligths.shp))




  cat(paste0("\n\n### ", wd, "\n\n"))

map <- tm_basemap(leaflet::providers$OpenStreetMap) +
  tmap_options(check.and.fix = TRUE) +
 tm_shape(wd) +
  tm_fill(col = "#1FC17B", alpha = 0.7) +
  tm_borders(col = "#808080")
tm_shape(ligths) +
    tm_dots(col = "#1FC17B", alpha = 0.7) +

map

  cat("\n\n\\newpage")
}

but even when it generates de headings it does not print the map

Answer 1

When you copy-paste code, as you mention, your goal is to iterate over different values of a variable in a for loop, as you state in the OP title; in R there are several ways to iterate, the example here uses lapply and for; to replicate as is, you should rbind your zone_x.shp files together:

library(tmap)
library(sf)

# call some sample data
data(World, metro, rivers)

# lets just do it for some countries in South America
latam = World[World$continent == "South America",]
latam = latam[1:5, ]

tmaps_list = lapply(latam$name,
              function(x){ 
                latam_f = latam[latam$name == x,] 
                riv_f = st_intersection(rivers, latam_f)
                tm_shape(latam_f, is.master = T) + tm_polygons() +
                tm_shape(riv_f) + tm_lines()})

# check whether items on the list are maps:
class(tmaps_list[[1]])
# [1] tmap

# each item in the list is a tmap object;
# we save it with tmap_save
for(i in seq_along(tmaps_list)) { 
  tmap_save(tmaps_list[[i]], filename = paste0(latam$name[i], ".png") )
  
  }