Compile multiple raster extractions to one table - r

Question

I have 3 rasters in which I have extracted data from using a polyline from a shapefile. Currently, I have the extraction as 3 separate lists. Is there A way I can do an extraction from all three rasters and compile them to one table with different columns for the data from each raster?
This is the current code I am using
Harney_Transects <- readOGR(dsn = ".", layer = "Transect_HN")
MeanTreeHeightHarneyBefore=raster('HN_TrMean_B_Clip.tif')
ScanAngleHarneyBefore= raster('HNScanAngle_B_Clip.tif')
MeanShrubHeightHarneyBefore= raster('HN_MeanShrub_B_Clip.tif')
Extraction_Shrub_Harney= extract(MeanShrubHeightHarneyBefore,Harney_Transects)
Extraction_Tree_Harney= extract(MeanTreeHeightHarneyBefore,Harney_Transects)
Extraction_ScanAngle_Harney= extract(ScanAngleHarneyBefore,Harney_Transects)

Answer 1

In short, you can stack() all the rasters you want to extract data from, and extract from the stack.
Here's a fully reproducible example using two rasters and a SpatialLines object, like you have in your question. Skip to the last code chunk for a direct answer to your question.
library(sp)
library(raster)
# function to generate random rasters
gen_raster <- function(){
r <- raster(nrows = 10, ncols = 10, res = 1,
xmn = 0, xmx = 10, ymn = 0, ymx = 10,
vals = rnorm(100, 5, 1))
return(r)
}
# generate 2 random rasters
r1 <- gen_raster()
r2 <- gen_raster()
# view
par(mfrow = c(1,2))
plot(r1, main = "raster 1"); plot(r2, main = "raster 2")
dev.off()
# generate transect (`SpatialLines` object)
m <- as.matrix(data.frame(x = 5.5, y = seq(0, 10, 1)))
l <- list(Lines(Line(m), "m"))
l <- SpatialLines(l)
# view the transect
plot(r1, main = "raster 1 with transect"); lines(l)
Running extract on the stacked rasters returns a list with a matrix in it. The last thing you'll want is to pull this out as a data.frame, which is a bit tricky.
rs <- stack(r1, r2) # stack any amount of rasters to extract from
re <- extract(rs, l) # extract at locations `l`
do.call(rbind.data.frame, re) # convert to data.frame
layer.1 layer.2
1 4.586890 5.115136
2 4.780503 5.093281
3 6.877302 3.337345
4 5.913230 3.755099
5 4.907834 4.887160
6 5.576908 5.386136
7 3.572350 5.225392
8 4.778727 5.391765
9 6.600041 4.205841
10 6.946321 5.544172
The names of the columns are the names of the raster layers in the stack. You can access these names with names(rs), and modify them with names(rs) <- c("new_name_1", "new_name_2").