You can either reproject your polygon shapefile OR your dataset. EPSG is a short code for spatial projections. EPSG:4326 is the code for non-projected data in degrees using wgs84: http://spatialreference.org/ref/epsg/4326/
Reproject your polygon into 4326
france_wgs84 <- spTransform(france_L93, CRS("+init=epsg:4326"))
Reproject your dataset into Lambert93
data <- structure(list(centerid = c("0121H1", "0121H2", "0218H3", "0303H1",
"0303H2"), latitude = c(46.2236804, 46.2236804, 49.3700842, 46.3429172,
46.3429172), longitude = c(5.2108193, 5.2108193, 3.335127, 2.6089958,
2.6089958), adresse_complete = c("900 Route de Paris, 01440 Viriat, France",
"900 Route de Paris, 01440 Viriat, France", "46 Avenue du Général de Gaulle, 02200 Soissons, France",
"18 Avenue du 8 Mai 1945, 03100 Montluçon, France", "18 Avenue du 8 Mai 1945, 03100 Montluçon, France"
)), .Names = c("centerid", "latitude", "longitude", "adresse_complete"
), row.names = c(NA, 5L), class = "data.frame")
coordinates(data) <- ~longitude+latitude
proj4string(data) <- "+init=epsg:4326"
data_L93 <- spTransform(data, CRS("+proj=lcc +lat_1=44 +lat_2=49 +lat_0=46.5 +lon_0=3 +x_0=700000 +y_0=6600000 +ellps=GRS80 +units=m
+no_defs"))
Best Answer
You can use "Rectangles, ovals, diamonds" tool. Make sure the unit is degrees. If you use this tool, each grid polygon will have all information of the related point, but possible.
Result:
In case of getting gap or overlap, "Snap geometries to layer" tool can be used to fix that issue after "Rectangle, ovals, diamonds" tool. I personally haven't encountered such an error unless the "Rotation" value is specified.