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Let's say I have two tasks with some duration in HH:MM format and value (points). I'd like to calculate the velocity (you can think of points as km and time in hours, you get km/h)

| task |     time | points | velocity |
|------+----------+--------+----------|
| A    |     0:45 |      2 | 2/0      |
| B    |     1:30 |      1 | 30       |
| Sum  | 02:15:00 |        | #ERROR   |
#+TBLFM: @4$2=vsum(@2..@3);T::$4=$3/$2

I can easily sum the duration adding ;T at the end of the sum formula (@4$2=vsum(@2..@3);T). However, the division of a number (the points in column 3) by a time in HH:MM format ($4=$3/$2) doesn't work out of the box.

How can I do it?

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7
  • In the final row, $3 is not defined, so $2/$3 does not make sense. Did you mean to specify it somehow?
    – NickD
    Commented Dec 20, 2021 at 14:39
  • Divide points by time? That does not make any sense to me. What do the "points" represent, what does the time represent and what are you trying to calculate?
    – NickD
    Commented Dec 21, 2021 at 0:11
  • @NickD it's a velocity measure. Think of points as of km. You made 20 km in 0:20 hours (i.e. in 20 minutes), your velocity ("ratio") is 60. With time duration and points is common in project management (prioritisation is given to the task with higher velocity).
    – Max Li
    Commented Dec 21, 2021 at 11:16
  • I was wondering about that. You should add that description in your question: if you had, we would not need all this discussion to get here.
    – NickD
    Commented Dec 21, 2021 at 14:27
  • You should also edit your question to fix it: ATM it's very misleading because the description ("... the division of HH:MM format by a number...") is the exact opposite of the operation ($3/$2).
    – NickD
    Commented Dec 21, 2021 at 15:00

1 Answer 1

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1

I think the problem is in the structure of the division so time/number give a result if you add ;T.

Instead of $3/$2 (ratio/time), try $2/$3 (time/ratio):

| task |     time | points |    ratio |
| ---- | -------- | ------ | -------- |
| A    |     0:45 |      2 | 00:22:30 |
| B    |     1:30 |      1 | 01:30:00 |
| Sum  | 02:15:00 |        | 01:52:30 |
#+tblfm: @4$2=vsum(@2$2..@3$2);T::@3$4=$2/$3;T::@4$4=vsum(@2$4..@3$4);T
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5
  • actually, $3/$2 instead of $2/$3 was a typo, sorry for that, in the table formula is was $2/$3. ";T" at the end of the formula worked indeed (i thought i tried it out). Thanks for the answer.
    – Max Li
    Commented Dec 20, 2021 at 14:23
  • It's not quite clear what the OP really wants, but the basic error in his formula is that $3 is not defined in the final row. You have modified his formula to something else, so I'm not sure you are answering his question - although the fact that he has accepted your answer has confused me :-)
    – NickD
    Commented Dec 20, 2021 at 14:41
  • @NickD thanks for formatting the tables. Looks like even without specifying $3 in the last row, the formula fills in $4 all the rows but the final one (for which it throws an error).
    – Max Li
    Commented Dec 20, 2021 at 15:19
  • The formula in the answer is different from the formula in the question, so I'm not sure which formula you are talking about.
    – NickD
    Commented Dec 20, 2021 at 15:45
  • @NickD actually, you were right that it wasn't clear that OP wants. I actually want to divide points by hour (I'll correct the question), and this doesn't work with ;T at the end of the division formula.
    – Max Li
    Commented Dec 20, 2021 at 22:51

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