lines crossing in a map with grids (ggplot) - r

Question

I've been having difficulties with a map I created in R. I'm trying to make a map with a grid where in each square, there's a value corresponding to a dataframe. So far, I made the shapefile and the script following some tutorials and posts from here (Download), but the final result got kinda weird.
library(xlsx)
library(ggplot2)
library(sp)
library(raster)
library(plyr)
library(dplyr)
library(tidyr)
library(sp)
library(raster)
library(rgeos)
library(rgbif)
library(viridis)
library(gridExtra)
library(rasterVis)
library(ggplot2)
library(maps)
library(rgdal)
br <- readOGR(choose.files(), "brgrid")
plot(br)
class(br)
str(br#data)
br#data$id <- rownames(br#data)
br.df <- fortify(br)
br.df <- join(br.df, br#data, by="id")
str(br.df)
tail(br.df)
names(br.df)
tail(br.df$id)
dados <- read.xlsx("ptsgrid.xlsx",6)
names(dados)
br.df <- merge(br.df, dados, by.x="id", by.y="id", all.x=T, a..ly=F)
str(br.df)
ggp <- ggplot(data=br.df, aes(x=long, y=lat, group=group))
ggp <- ggp + geom_polygon(aes(fill=value)) # draw polygons
ggp <- ggp + geom_path(color="grey", linestyle=1) # draw boundaries
ggp <- ggp + coord_equal()
ggp <- ggp + scale_fill_gradient(low = "#ffffcc", high = "#ff4444",
space = "Lab", na.value = "grey50",
guide = "colourbar")
print(ggp)
I want to know why the lines got crossed in the map, and how to fix it. Also, I wanna know if it's possible to omit some squares (I only have interest in coastal region, so it'll look better if I omit the rest). And finally, I don't know why the map boundaries got "overlayed" (maybe a projection issue?).

Answer 1

Welcome to Stack Overflow! What have you done so far/what does your code look like? I will share with you a map/code I made that functions as I intended, so you can replace values in my code with what you need for your needs/with your data Below is code for a map I created in R for income in the United States:
library(maps)
library(ggplot2)
usa=map_data("state")
ggplot(usa)+geom_polygon(aes(x=long,y=lat,group=group,fill=region),color="white")+coord_fixed(1.3)+guides(fill=FALSE,color=FALSE)
The result of the above code:

Answer 2

I downloaded your data set. I did not examine your code. But I think when you created br.df using merge(), order got messed up. In your code, I am talking about this line (br.df<-merge(br.df, dados, by.x="id", by.y="id", all.x=T, a..ly=F). You may want to check this question. You wanted to combine all data sets. But you do not have to do that.
In your data set, dados, you have 148 data points. But you have 150 grids in your map data. So I modified your EXCEL data; I added id = 0 and id = 149. Each data point has 0 and 495, respectively. As long as there is a common column name (in this case, id), you can do the following. I used geom_cartogram() in the ggalt package. The second geom_cartogram() is adding colors to the grids.
library(rgdal)
library(ggplot2)
library(ggalt)
library(readxl)
# Create a map data
foo <- readOGR(dsn = "brgrid.shp")
mygrid <- fortify(foo)
# Import the EXCEL data
dados <- read_excel("ptsgrid.xlsx", sheet = 6)
ggplot() +
geom_cartogram(data = mygrid, map = mygrid,
aes(x = long, y = lat, map_id = id),
color = "black", alpha = 0.5) +
geom_cartogram(data = dados, map = mygrid,
aes(fill = value, map_id = id)) +
scale_fill_gradient(low = "#ffffcc", high = "#ff4444",
space = "Lab", na.value = "grey50",
guide = "colourbar")