library(ggplot2)
library(gstat)
library(sp)
library(maptools)
library(rgdal)
library(zoo)
library(xts)
library(RPostgreSQL)
library(spacetime)
library(raster)
library(foreign)
dbname = "postgis"
user = "postgres"
password = "***"
#password = ""

drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname="BDDMeteo", user=user, password="***",host='localhost', port='5432')
estonia_air_temperature_2=dbGetQuery(con,"select lat,lon,temperature from observation, station, date where id_s=nom_ville AND id_d=id_date")

estonia_air_temperature_2_test <- estonia_air_temperature_2  # duplicate air temp. data file
estonia_air_temperature_2_test$x <- estonia_air_temperature_2_test$lon  # define x & y as longitude and latitude
estonia_air_temperature_2_test$y <- estonia_air_temperature_2_test$lat
coordinates(estonia_air_temperature_2_test) = ~x + y

plot(estonia_air_temperature_2_test)
x.range <- as.numeric(c(-8.5, 9.5))  # min/max longitude of the interpolation area
y.range <- as.numeric(c(26.97, 37))  # min/max latitude of the interpolation area
grd <- expand.grid(x = seq(from = x.range[1], to = x.range[2], by = 0.1), y = seq(from = y.range[1],
                                                                                  to = y.range[2], by = 0.1))  # expand points to grid
coordinates(grd) <- ~x + y
gridded(grd) <- TRUE
plot(grd, cex = 1.5, col = "grey")
points(estonia_air_temperature_2_test, pch = 1, col = "red", cex = 0.4)

idw <- idw(formula = temperature ~ 1, locations = estonia_air_temperature_2_test,
           newdata = grd)  # apply idw model for the data
residual_grid = raster(idw, "var1.pred")
plot(residual_grid)
x <- rasterToContour(residual_grid)
class(x)
plot(residual_grid)
plot(x, add=TRUE)
writeSpatialShape(x, "/interpolate/contour/contourline")

> ogrDrivers()
             name write
1      AeronavFAA FALSE
2          ARCGEN FALSE
3          AVCBin FALSE
4          AVCE00 FALSE
5             BNA  TRUE
6             CSV  TRUE
7             DGN  TRUE
8             DXF  TRUE
9          EDIGEO FALSE
10 ESRI Shapefile  TRUE
11     Geoconcept  TRUE
12        GeoJSON  TRUE
13       Geomedia FALSE
14         GeoRSS  TRUE
15            GML  TRUE
16            GMT  TRUE
17       GPSBabel  TRUE
18  GPSTrackMaker  TRUE
19            GPX  TRUE
20            HTF FALSE
21         Idrisi FALSE
22            KML  TRUE
23   MapInfo File  TRUE
24         Memory  TRUE
25   MSSQLSpatial  TRUE
26           ODBC  TRUE
27            ODS  TRUE
28        OpenAir FALSE
29    OpenFileGDB FALSE
30         PCIDSK  TRUE
31            PDF  TRUE
32            PDS FALSE
33         PGDump  TRUE
34           PGeo FALSE
35            REC FALSE
36            S57  TRUE
37           SDTS FALSE
38       SEGUKOOA FALSE
39           SEGY FALSE
40            SUA FALSE
41            SVG FALSE
42            SXF FALSE
43          TIGER  TRUE
44        UK .NTF FALSE
45            VRT FALSE
46           Walk FALSE
47           WAsP  TRUE
48           XLSX  TRUE
49         XPlane FALSE

#R code assumes library(rgdal)
writeOGR(x, "PG:dbname='BDDMeteo' user=user password="zina",host='localhost', port='5432' ", layer_options = "geometry_name=geom",
"newtablename", "PostgreSQL")