readtable() function cannot be manually told the spreadsheet column data format.
'%s %f' option ONLY applies to text files.
Fix your spreadsheet (.xls, .ods) where an all-numeric column is being read as text in cells:
- highlight that entire column
- select Format Cells, Number.
Microsoft Excel has that handy green alert triangle if you do this (store a number as text).
Note: it is permissible to have the first row of an all-numeric column be a text header.