So I've created a file that reads into a data frame in the same way as yours:
> str(v2)
'data.frame': 360 obs. of 720 variables:
BUT data.frame isn't really the right thing here. Its really meant for record-oriented data, where each row is a record and each column is a potentially different variable for that record (eg each row is a person, the columns are name, age, height, etc).
So you really only need to scan
the data in as one long vector and feed it to a raster.
Step 1, define an empty raster of the right size and shape (note I'm assuming the raster covers the whole world, so the limits are not the cell centres):
> m2=raster(nrow=360,ncol=720,xmn=-180,xmx=180,ymn=-90,ymx=90)
Step 2, read numeric values into the raster data slot:
> m2[]=scan("d.txt",what=1)
Read 259200 items
And give it a projection if needed:
> projection(m2)="+init=epsg:4326"
> plot(m2)
If you want to check that the resolution and the cell centres are as expected, use these functions:
> res(m2)
[1] 0.5 0.5
> xFromCol(m2,1:10)
[1] -179.75 -179.25 -178.75 -178.25 -177.75 -177.25 -176.75 -176.25 -175.75
[10] -175.25
> yFromRow(m2,1:10)
[1] 89.75 89.25 88.75 88.25 87.75 87.25 86.75 86.25 85.75 85.25
which shows the resolution is half a degree and the cell centres (or at least the first 10) are at those specified coordinates.
I noticed the Mosaic To New Raster tool has a Mosaic Operator setting. The default is LAST, which states the output cell value of the overlapping areas will be the value from the last raster dataset mosaicked into that location. Settings are FIRST, LAST, BLEND, MEAN, MINIMUM, and MAXIMUM. I would try other settings or reorder your rasters in the Input Rasters list.
Best Answer
If you would like to keep the object type(s) as raster I would take a look at the ratify function although, I do not think that it is intended for numeric data.
You could also coerce the raster brick object to a SpatialPixelsDataFrame object where the @data slots holds attributes for each raster. This is however, not necessarily memory safe.