Fortran splats my output to asterisks - why?
formatting, fortran, io
Solution
Fortran format statements are defined as:
`Fw.d`, where w is the number of characters to be used in total, and d is the number of characters after the decimal point. Here you are telling it that you need a float, that is 1 character wide in total, and 2 characters after the decimal point, something that is obviously not correct. So to get, for example, a float that is 4 characters in total, with 3 decimal places, you'd write:
write(*, '(F4.3)') t*1E9
See http://www.cs.mtu.edu/~shene/COURSES/cs201/NOTES/chap05/format.html
Also, I should mention that the asterisks are indicative that the number cannot be displayed in the format stated.
EDIT:
Adding in the comment from george below:
"For E format the fieldwidth has to be at least 7 more than the number of decimals, eg E15.8. Four for the exponent, two for the lead 0. one for a possible '-'. I usually add one more extra space so numbers don't run together, E16.8"
Problem
I'm having a hard time wrapping my head around formatting statements in Fortran. Without formatting my output, this is what I do (inside a loop, so this happens a few times): ``` write(*,*) t*1E9 ``` `t` here is `real*8`. The output is just what I'd expect - increments of 0.1, with some rounding errors: ``` 0.0000000000000000 0.10000000000000001 0.20000000000000001 0.29999999999999999 0.40000000000000002 0.50000000000000000 0.59999999999999998 0.69999999999999996 0.79999999999999993 0.89999999999999991 0.99999999999999989 ``` Now, I try to add a format statement: ``` write(*, '(F1.2)') t*1E9 ``` and (with everything else the same) instead I get only asterisks in my output: ``` ** ** (etc...) ``` I've tried to read up on how this should work, and I can't figure out why this is happening. I've tried formats with more space for digits (`F15.15` just gives me more asterisks per line), I've tried moving the format statement to its own, labelled line... I just can't seem to get the output I'd like. What am I missing here?