r - Mapping several maps with the same colorscheme in tmap

How to control the dot colors in tmap? I have the following code:

png(filename = "test.png", 

    width = 210, height = 297, units = "mm", pointsize = 1,
    bg = "white", res = 1200)
for (j in 2012:2016){
t <- tm_shape(n2000) +
  tm_borders("black") +
  tm_shape(dk) + 
  tm_fill("grey30") +
  tm_borders("grey70") +
  tm_shape(out3[out3$Country==i & out3$Year == j,]) +
  tm_dots("LE_GEAR",            

          size = 1, title=paste0("Type , ", i, ", ", j)) +
   tm_legend(text.size=10,
            title.size=12,            
            position = c("left","top"), 
            bg.color = "white", 
            bg.alpha=.2, 
            frame="gray50", 
            height=.6, 
            hist.width=20,
            hist.height=20, 

            hist.bg.color="gray60", 
            hist.bg.alpha=.5) +
  tm_shape(Labels) +
  tm_text("Name", size = 4) 

assign(paste0("t", j), t)
}

tm <- tmap_arrange(t2012, t2013, t2014, t2015, t2016)#, asp = NA)


graphics.off()

Which gives me the map below. The problem is that the colors for for example GNS is different from 2012 to the other years. How can i make sure the colors are the same?

Answer

The trick is to create a custom color palette. First, a reproducible example:

library(sp)
library(tmap)

data(meuse, meuse.area)       


coordinates(meuse) <- ~x + y 

meuse.area <- SpatialPolygons(list(Polygons(list(Polygon(meuse.area)),'1')))

proj4string(meuse)<- CRS("+init=epsg:28992")
proj4string(meuse.area)<- CRS("+init=epsg:28992")

set.seed(123)


# Package example
require(tmaptools)
data(World)
x <- sample_dots(World, vars="gdp_md_est", convert2density = TRUE, w = 100000)
x <- SpatialPointsDataFrame(x, data.frame(type=factor(sample(1:5,size=length(x),replace = T))))

tm_shape(x) + 
  tm_dots()

Identify unique features prior to create a color palette. I used rainbow color function, but you can choose your own colors in hex format.

# To set color, first identify unique features
types <- unique(x$type)
types <- sort(types)

# asssigg one color per feature (I used rainbow for hex colors)
color_type <- rainbow(length(types))

# Use the above color palette
tm_shape(x) + 

  tm_dots('type',palette=color_type)

Finally, use this information to set the color palette en each iteration.

for(i in 1:5){
  temp <- x[x@data$type==types[i],]
  temp$type  <- droplevels(temp$type)
  t <- tm_shape(temp) + 
    tm_dots('type',palette=color_type[i])
  assign(paste0('t',i),t)

}

tmap_arrange(t1,t2,t3,t4,t5)

So, in your case, you need to identify which feature is present by year and select the right color schema. Something like:

classes <- unique(out3$LE_GEAR)
classes <- sort(classes)
classcolor <- rainbow(length(classes))


for (j in 2012:2016){
  temp <- out3[out3$Country==i & out3$Year == j,]
  temp$LE_GEAR <- droplevels(temp$LE_GEAR)
  actual_classes <- unique(temp$LE_GEAR)
  actual_classes <- sort(actual_classes)
  t <- tm_shape(n2000) +
    tm_borders("black") +
    tm_shape(dk) + 
    tm_fill("grey30") +
    tm_borders("grey70") +

    tm_shape(temp) +
    tm_dots("LE_GEAR",            
            size = 1, title=paste0("Type , ", i, ", ", j),
            palette=classcolor[match(actual_classes,classes)]) +
    tm_legend(text.size=10,
              title.size=12,            
              position = c("left","top"), 
              bg.color = "white", 
              bg.alpha=.2, 
              frame="gray50", 

              height=.6, 
              hist.width=20,
              hist.height=20, 
              hist.bg.color="gray60", 
              hist.bg.alpha=.5) +
    tm_shape(Labels) +
    tm_text("Name", size = 4) 

  assign(paste0("t", j), t)
}


tm <- tmap_arrange(t2012, t2013, t2014, t2015, t2016)

Hope this helps you... Without sample data, I can't help you better. I suppose j is a nested loop and i is the parent (not present in the code you give us)