Hi, and welcome!
Thanks for posting the code. It is always helpful, though, to use a reproducible example, called a reprex.
Although df_All is easy enough to replicate by hand by cutting and pasting into a csv then
library(tidyverse) # interactive session
df_All <- read.csv("~/Desktop/dfAll.csv", header = TRUE)
df_All
#> B1 B2 B3 B4 B5 B6 B7 class
#> 1 445 637 993 1197 2679 3387 2409 1
#> 2 525 636 948 1078 2613 3256 2517 1
#> 3 604 733 1049 1229 3377 3504 2891 1
#> 4 490 583 954 1359 3113 3742 2886 1
#> 5 216 292 535 620 2274 2327 1299 1
Created on 2019-11-18 by the reprex package (v0.3.0)
img and trainData_crs_utm aren't, and they are numeric values that are used in the cast to ms, and it's uncertain what a good guess would be. But I'll pick numbers out of a hat.
An aside: df is the name of a built in function:
df
#> function (x, df1, df2, ncp, log = FALSE)
#> {
#> if (missing(ncp))
#> .Call(C_df, x, df1, df2, log)
#> else .Call(C_dnf, x, df1, df2, ncp, log)
#> }
#> <bytecode: 0x7fad326c3758>
#> <environment: namespace:stats>
Created on 2019-11-18 by the reprex package (v0.3.0)
and it's good practice to avoid using it for an assignment result; my_df or even df. is preferable.
Aside: df <- round(dfAll) doesn't do anything.
library(tidyverse) # interactive session
df_All <- read.csv("~/Desktop/dfAll.csv", header = TRUE)
df_All == round(df_All)
#> B1 B2 B3 B4 B5 B6 B7 class
#> [1,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
#> [2,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
#> [3,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
#> [4,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
#> [5,] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
On to the cast.
Created on 2019-11-18 by the reprex package (v0.3.0)
library(tidyverse) # interactive session
df_All <- read.csv("~/Desktop/dfAll.csv", header = TRUE)
ms <- matrix(NA, nrow = 7, ncol = 7)
ms
#> [,1] [,2] [,3] [,4] [,5] [,6] [,7]
#> [1,] NA NA NA NA NA NA NA
#> [2,] NA NA NA NA NA NA NA
#> [3,] NA NA NA NA NA NA NA
#> [4,] NA NA NA NA NA NA NA
#> [5,] NA NA NA NA NA NA NA
#> [6,] NA NA NA NA NA NA NA
#> [7,] NA NA NA NA NA NA NA
Created on 2019-11-18 by the reprex package (v0.3.0)
It turns out that any nrow or ncol will have the same problem: all colMeans will be identically NA
library(tidyverse) # interactive session
df_All <- read.csv("~/Desktop/dfAll.csv", header = TRUE)
ms <- matrix(NA, nrow = 7, ncol = 7)
colMeans(ms)
#> [1] NA NA NA NA NA NA NA
Created on 2019-11-18 by the reprex package (v0.3.0)
Fix this and supply a reprex if you hit a bump again.
Finally, should this be homework, see the FAQ