Estimate ranges in column view

Carsten,
Here is a patch for a new 'est+' summary type, including corresponding changes for xemacs and the manual. I've done basic testing on the GNU emacs version, but not the xemacs code.

I'm not sure the change to the manual provides the right amount of information
in the right place; I'd be happy to re-write to make it find in
better. Similarly, the name of the summary type is entirely up to you.

I didn't know whether to send this directly to you, or to the list; if it should go to the list I'd be happy to send it there directly.

Thanks for the chance to contribute,
Mike

doc/org.texi

@@ -4755,9 +4755,10 @@ optional.  The individual parts have the following meaning:
                 @{:min@}    @r{Smallest time value in column.}
                 @{:max@}    @r{Largest time value.}
                 @{:mean@}   @r{Arithmetic mean of time values.}
-                @{@@min@}   @r{Minimum age (in days/hours/mins/seconds).}
-                @{@@max@}   @r{Maximum age (in days/hours/mins/seconds).}
-                @{@@mean@}  @r{Arithmetic mean of ages (in days/hours/mins/seconds).}
+                @{@@min@}    @r{Minimum age (in days/hours/mins/seconds).}
+                @{@@max@}    @r{Maximum age (in days/hours/mins/seconds).}
+                @{@@mean@}   @r{Arithmetic mean of ages (in days/hours/mins/seconds).}
+                @{est+@}    @r{Add low-high estimates.}
 @end example
 
 @noindent
@@ -4765,6 +4766,22 @@ Be aware that you can only have one summary type for any property you
 include. Subsequent columns referencing the same property will all display the
 same summary information.
 
+The 'est+' summary type requires further explanation. It is used for
+combining task estimates, expressed as low-high ranges. For example, instead
+of estimating a particular task will take 5 days, you might estimate it as
+5-6 days if you're fairly confident you know how much woark is required, or
+1-10 days if you don't really know what needs to be done.  Both ranges
+average at 5.5 days, but the first represents a more predictable delivery.
+
+When combining a set of such estimates, simply adding the lows and highs
+produces an unrealistically wide result. Instead, 'est+' adds the statistical
+mean and variance of the sub-tasks, generating a final estimate from the sum.
+For example, suppose you had ten tasks, each of which was estimated at 0.5 to
+2 days of work. Straight addition produces an estimate of 5 to 20 days,
+representing what to expect if everything goes either extremely well or
+extremely poorly. In contrast, 'est+' estimates the full job more
+realistically, at 10-15 days.
+
 Here is an example for a complete columns definition, along with allowed
 values.
 

lisp/org-colview-xemacs.el

@@ -917,7 +917,8 @@ around it."
     ("@max" max_age max (lambda (x) (- org-columns-time x)))
     ("@mean" mean_age
      (lambda (&rest x) (/ (apply '+ x) (float (length x))))
-     (lambda (x) (- org-columns-time x))))
+     (lambda (x) (- org-columns-time x)))
+    ("est+" estimate org-estimate-combine))
   "Operator <-> format,function,calc  map.
 Used to compile/uncompile columns format and completing read in
 interactive function `org-columns-new'.
@@ -1206,6 +1207,7 @@ Don't set this, this is meant for dynamic scoping.")
 (defun org-columns-number-to-string (n fmt &optional printf)
   "Convert a computed column number to a string value, according to FMT."
   (cond
+   ((memq fmt '(estimate)) (org-estimate-print n printf))
    ((not (numberp n)) "")
    ((memq fmt '(add_times max_times min_times mean_times))
     (let* ((h (floor n)) (m (floor (+ 0.5 (* 60 (- n h))))))
@@ -1250,9 +1252,9 @@ Don't set this, this is meant for dynamic scoping.")
 	    (setq sum (+ (string-to-number (pop l)) (/ sum 60))))
 	  sum))
        ((memq fmt '(checkbox checkbox-n-of-m checkbox-percent))
-	(if (equal s "[X]") 1. 0.000001))
-       (t (string-to-number s)))
-    0))
+        (if (equal s "[X]") 1. 0.000001))
+       ((memq fmt '(estimate)) (org-string-to-estimate s))
+       (t (string-to-number s)))))
 
 (defun org-columns-uncompile-format (cfmt)
   "Turn the compiled columns format back into a string representation."
@@ -1692,6 +1694,42 @@ This will add overlays to the date lines, to show the summary for each day."
       (format "%dd %02dh %02dm %02ds" days hours minutes seconds))
     ""))
 
+(defun org-estimate-mean-and-var (v)
+  "Return the mean and variance of an estimate."
+  (let* ((low (float (car v)))
+         (high (float (cadr v)))
+         (mean (/ (+ low high) 2.0))
+         (var (/ (+ (expt (- mean low) 2.0) (expt (- high mean) 2.0)) 2.0)))
+    (list  mean var)
+    ))
+
+(defun org-estimate-combine (&rest el)
+  "Combine a list of estimates, using mean and variance.
+The mean and variance of the result will be the sum of the means
+and variances (respectively) of the individual estimates."
+  (let ((mean 0)
+        (var 0))
+    (mapc (lambda (e)
+	    (let ((stats (org-estimate-mean-and-var e)))
+	      (setq mean (+ mean (car stats)))
+	      (setq var (+ var (cadr stats)))))
+	  el)
+    (let ((stdev (sqrt var)))
+      (list (- mean stdev) (+ mean stdev)))
+    ))
+
+(defun org-estimate-print (e &optional fmt)
+  "Prepare a string representation of an estimate, as two numbers with a '-' in between them."
+  (if (null fmt) (set 'fmt "%.0f"))
+  (format "%s" (mapconcat (lambda (n) (format fmt n))  e "-")))
+
+(defun org-string-to-estimate (s)
+  "Convert a string to an estimate. The string should be two numbers joined with a '-'."
+  (if (string-match "\\(.*\\)-\\(.*\\)" s)
+      (list (string-to-number (match-string 1 s)) (string-to-number(match-string 2 s)))
+    (list (string-to-number s) (string-to-number s))
+    ))
+
 
 (provide 'org-colview)
 (provide 'org-colview-xemacs)

lisp/org-colview.el

@@ -746,7 +746,8 @@ around it."
     ("@max" max_age max (lambda (x) (- org-columns-time x)))
     ("@mean" mean_age
      (lambda (&rest x) (/ (apply '+ x) (float (length x))))
-     (lambda (x) (- org-columns-time x))))
+     (lambda (x) (- org-columns-time x)))
+    ("est+" estimate org-estimate-combine))
   "Operator <-> format,function,calc  map.
 Used to compile/uncompile columns format and completing read in
 interactive function `org-columns-new'.
@@ -1031,6 +1032,7 @@ Don't set this, this is meant for dynamic scoping.")
 (defun org-columns-number-to-string (n fmt &optional printf)
   "Convert a computed column number to a string value, according to FMT."
   (cond
+   ((memq fmt '(estimate)) (org-estimate-print n printf))
    ((not (numberp n)) "")
    ((memq fmt '(add_times max_times min_times mean_times))
     (let* ((h (floor n)) (m (floor (+ 0.5 (* 60 (- n h))))))
@@ -1054,28 +1056,30 @@ Don't set this, this is meant for dynamic scoping.")
       (format "[%d/%d]" n m)
     (format "[%d%%]"(floor (+ 0.5 (* 100. (/ (* 1.0 n) m)))))))
 
+
 (defun org-columns-string-to-number (s fmt)
   "Convert a column value to a number that can be used for column computing."
   (if s
       (cond
        ((memq fmt '(min_age max_age mean_age))
-	(cond ((string= s "") org-columns-time)
-	      ((string-match
-		"\\([0-9]+\\)d \\([0-9]+\\)h \\([0-9]+\\)m \\([0-9]+\\)s"
-		s)
-	       (+ (* 60 (+ (* 60 (+ (* 24 (string-to-number (match-string 1 s)))
-				    (string-to-number (match-string 2 s))))
-			   (string-to-number (match-string 3 s))))
-		  (string-to-number (match-string 4 s))))
-	      (t (time-to-number-of-days (apply 'encode-time
-						(org-parse-time-string s t))))))
+        (cond ((string= s "") org-columns-time)
+              ((string-match
+                "\\([0-9]+\\)d \\([0-9]+\\)h \\([0-9]+\\)m \\([0-9]+\\)s"
+                s)
+               (+ (* 60 (+ (* 60 (+ (* 24 (string-to-number (match-string 1 s)))
+                                    (string-to-number (match-string 2 s))))
+                           (string-to-number (match-string 3 s))))
+                  (string-to-number (match-string 4 s))))
+              (t (time-to-number-of-days (apply 'encode-time
+                                                (org-parse-time-string s t))))))
        ((string-match ":" s)
-	(let ((l (nreverse (org-split-string s ":"))) (sum 0.0))
-	  (while l
-	    (setq sum (+ (string-to-number (pop l)) (/ sum 60))))
-	  sum))
+        (let ((l (nreverse (org-split-string s ":"))) (sum 0.0))
+          (while l
+            (setq sum (+ (string-to-number (pop l)) (/ sum 60))))
+          sum))
        ((memq fmt '(checkbox checkbox-n-of-m checkbox-percent))
-	(if (equal s "[X]") 1. 0.000001))
+        (if (equal s "[X]") 1. 0.000001))
+       ((memq fmt '(estimate)) (org-string-to-estimate s))
        (t (string-to-number s)))))
 
 (defun org-columns-uncompile-format (cfmt)
@@ -1491,6 +1495,43 @@ This will add overlays to the date lines, to show the summary for each day."
       (format "%dd %02dh %02dm %02ds" days hours minutes seconds))
     ""))
 
+(defun org-estimate-mean-and-var (v)
+  "Return the mean and variance of an estimate."
+  (let* ((low (float (car v)))
+         (high (float (cadr v)))
+         (mean (/ (+ low high) 2.0))
+         (var (/ (+ (expt (- mean low) 2.0) (expt (- high mean) 2.0)) 2.0)))
+    (list  mean var)
+    ))
+
+(defun org-estimate-combine (&rest el)
+  "Combine a list of estimates, using mean and variance.
+The mean and variance of the result will be the sum of the means
+and variances (respectively) of the individual estimates."
+  (let ((mean 0)
+        (var 0))
+    (mapc (lambda (e)
+              (let ((stats (org-estimate-mean-and-var e)))
+                (setq mean (+ mean (car stats)))
+                (setq var (+ var (cadr stats)))))
+            el)
+    (let ((stdev (sqrt var)))
+      (list (- mean stdev) (+ mean stdev)))
+    ))
+
+(defun org-estimate-print (e &optional fmt)
+  "Prepare a string representation of an estimate, as two numbers with a '-' in between them."
+  (if (null fmt) (set 'fmt "%.0f"))
+  (format "%s" (mapconcat (lambda (n) (format fmt n))  e "-"))
+  )
+
+(defun org-string-to-estimate (s)
+  "Convert a string to an estimate. The string should be two numbers joined with a '-'."
+  (if (string-match "\\(.*\\)-\\(.*\\)" s)
+      (list (string-to-number (match-string 1 s)) (string-to-number(match-string 2 s)))
+    (list (string-to-number s) (string-to-number s))
+    ))
+
 
 (provide 'org-colview)