Coords_convert.Rmd

---
title: "Coordinate conversion in R"
output: html_document
---


## R Script for converting coordinates (e.g., UTM to Lat/Long).


### Required packages
```{r }
library(sp)
library(maptools)
```


### Load data table
```{r load}

# Receptors in UTM
data <- read.csv("M:\\MNRiskS 2011 development\\Receptors\\Backup receptors\\LAKES receptors used in MNRISKS 2011.csv", stringsAsFactors = F)[ , -c(4:5)]

# Show first rows
head(data)
```


| Receptor|        GEOID| FIPS_Code|    utm_x|   utm_y| zoneID|County |  
|--------:|------------:|---------:|--------:|-------:|------:|:------|  
|    46318| 270017701001|         1| 490997.4| 5174001|  27001|AITKIN |  
|    46383| 270017701001|         1| 494000.8| 5173997|  27001|AITKIN |   
|    46514| 270017701001|         1| 491001.9| 5177001|  27001|AITKIN |  
|    46526| 270017701001|         1| 475999.8| 5176998|  27001|AITKIN |  
|    46579| 270017701001|         1| 467001.5| 5176996|  27001|AITKIN |   
|    46591| 270017701001|         1| 493996.2| 5176997|  27001|AITKIN | 
  
### Convert to shapefile
```{r shapefile}
coordinates(data) <- ~utm_x + utm_y

```

### Assign current projection
```{r projection}

# NAD83 / UTM zone 15N
proj4string(data) <- CRS("+init=epsg:26915") 

# Alternative projections:
# WGS84 Web Mercator (Auxiliary Sphere) -> CRS("+init=epsg:3857")
# WGS 84 -> CRS("+init=epsg:4326")

```


### Plot shapefile
```{r plot}
plot(data)

```

### Transform projection
```{r transform coordinates}
data_new  <- spTransform(data , CRS("+init=epsg:4326"))

```

### Plot new data
```{r plot_new}
plot(data_new)

```


### Convert shapefile back to data table
```{r back to data frame}
data_new  <- data.frame(data_new, stringsAsFactors = F)

# Show first rows
head(data_new)

# Re-name coordinate columns to lat/long
names(data_new)[7:6] <- c("Lat", "Long")

```


### Save new coordinates as .CSV
```{r save}
write.csv(data_new, "Transformed receptors.csv", row.names=F)

```