I have 7 datasets, I need to plot a t-SNE and color the samples by dataset. All of them have the exact same rows but different columns (and different number of columns). I joined the 7 dataframes into one, using cbind.

How can I do that ?

This is sample for one of the dataframe using dput - columns are the samples and rows are cell types:

cells1 <- structure(c(8.10937548981953e-20, 0.095381661829093, 0.054868371418562, 
0.0523687378840825, 0.0100173293159538, 0.0332395245437795, 3.37811149975583e-20, 
0.048191378909587, 0.13314908462763, 0, 0.00612878313809124, 
0, 0.00117409520254045, 1.33684197233784, 0.0701023734195797, 
0.290756813286141, 0.349392264371762, 0.169367429138566, 0.00209460699328093, 
0.205599458004829, 0.318048653115709, 4.21796249339787e-05, 0.00844407692255898, 
0, 0.00613007026042523, 0.0300024082993193, 0.0405191646567986, 
0.00654087887823056, 0.0111094954094255, 1.30617589099212e-19, 
0.0398730537850546, 0.0390946117756341, 0.239413780024853, 2.07521807718399e-19, 
0.00116980239850497, 0), .Dim = c(6L, 6L), .Dimnames = list(c("Adipocytes", 
"B-cells", "Basophils", "CD4+ memory T-cells", "CD4+ naive T-cells", 
"CD4+ T-cells"), c("Pt1", "Pt10", "Pt101", "Pt103", "Pt106", 
"Pt11")))