Confused on conversions with averages

[jimmykane]

Hi @thomaschampagne I might need your help here.

I am having some calc inconsistency when trying to figure out some averages. Apparently I am doing something wrong, but I cannot figure it out.

I have an array of speed samples example:

[
  3.3,
  3.3,
  3.32,
  3.32,
  3.22,
  3.22,
  3.14,
  3.14,
  3,
  3,
  3,
  3,
  3.02,
  3.02,
  2.96,
  2.96,
  2.92,
  2.92,
  2.88,
  2.88,
  2.88,
  2.88,
  2.86,
  2.86,
  2.86,
  2.86,
  2.86,
  2.86,
  2.88,
  2.88,
  2.88,
  2.88,
  2.86,
  2.86,
  2.84,
  2.84,
  2.86,
  2.86,
  2.88,
  2.88,
  2.9,
  2.9,
  2.86,
  2.86,
  2.84,
  2.84,
  2.84,
  2.84,
  2.82,
  2.82,
  2.8,
  2.8,
  2.64,
  2.64,
  0,
  0,
  2.22,
  2.22,
  2.3,
  2.3,
  2.4,
  2.4,
  2.44,
  2.44,
  2.58,
  2.58,
  2.6,
  2.6,
  2.62,
  2.62,
  2.62,
  2.62,
  2.58,
  2.58,
  2.54,
  2.54,
  2.52,
  2.52,
  2.5,
  2.5,
  2.5,
  2.5,
  2.5,
  2.5,
  2.48,
  2.48,
  2.46,
  2.46,
  2.44,
  2.44,
  2.44,
  2.44,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42
]

Now in order to find the average speed I do

[
  3.3,
  3.3,
  3.32,
  3.32,
  3.22,
  3.22,
  3.14,
  3.14,
  3,
  3,
  3,
  3,
  3.02,
  3.02,
  2.96,
  2.96,
  2.92,
  2.92,
  2.88,
  2.88,
  2.88,
  2.88,
  2.86,
  2.86,
  2.86,
  2.86,
  2.86,
  2.86,
  2.88,
  2.88,
  2.88,
  2.88,
  2.86,
  2.86,
  2.84,
  2.84,
  2.86,
  2.86,
  2.88,
  2.88,
  2.9,
  2.9,
  2.86,
  2.86,
  2.84,
  2.84,
  2.84,
  2.84,
  2.82,
  2.82,
  2.8,
  2.8,
  2.64,
  2.64,
  0,
  0,
  2.22,
  2.22,
  2.3,
  2.3,
  2.4,
  2.4,
  2.44,
  2.44,
  2.58,
  2.58,
  2.6,
  2.6,
  2.62,
  2.62,
  2.62,
  2.62,
  2.58,
  2.58,
  2.54,
  2.54,
  2.52,
  2.52,
  2.5,
  2.5,
  2.5,
  2.5,
  2.5,
  2.5,
  2.48,
  2.48,
  2.46,
  2.46,
  2.44,
  2.44,
  2.44,
  2.44,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42,
  2.42
].reduce(function(acc, val) { return acc + val; }, 0)/100

The result is: (m/s)

2.670800000000001

Now to convert to pace I do

1000/2.670800000000001 = 374.41964954320787

So 374.41964954320787 seconds

Now if I first convert that array of speed values to pace with the same conversion like

speedArray.map(v => 1000/v)

I get this array

[
  303.03030303030306,
  303.03030303030306,
  301.20481927710847,
  301.20481927710847,
  310.55900621118013,
  310.55900621118013,
  318.4713375796178,
  318.4713375796178,
  333.3333333333333,
  333.3333333333333,
  333.3333333333333,
  333.3333333333333,
  331.12582781456956,
  331.12582781456956,
  337.83783783783787,
  337.83783783783787,
  342.4657534246575,
  342.4657534246575,
  347.22222222222223,
  347.22222222222223,
  347.22222222222223,
  347.22222222222223,
  349.65034965034965,
  349.65034965034965,
  349.65034965034965,
  349.65034965034965,
  349.65034965034965,
  349.65034965034965,
  347.22222222222223,
  347.22222222222223,
  347.22222222222223,
  347.22222222222223,
  349.65034965034965,
  349.65034965034965,
  352.11267605633805,
  352.11267605633805,
  349.65034965034965,
  349.65034965034965,
  347.22222222222223,
  347.22222222222223,
  344.82758620689657,
  344.82758620689657,
  349.65034965034965,
  349.65034965034965,
  352.11267605633805,
  352.11267605633805,
  352.11267605633805,
  352.11267605633805,
  354.6099290780142,
  354.6099290780142,
  357.14285714285717,
  357.14285714285717,
  378.78787878787875,
  378.78787878787875,
  Infinity,
  Infinity,
  450.45045045045043,
  450.45045045045043,
  434.7826086956522,
  434.7826086956522,
  416.6666666666667,
  416.6666666666667,
  409.8360655737705,
  409.8360655737705,
  387.5968992248062,
  387.5968992248062,
  384.6153846153846,
  384.6153846153846,
  381.6793893129771,
  381.6793893129771,
  381.6793893129771,
  381.6793893129771,
  387.5968992248062,
  387.5968992248062,
  393.7007874015748,
  393.7007874015748,
  396.8253968253968,
  396.8253968253968,
  400,
  400,
  400,
  400,
  400,
  400,
  403.2258064516129,
  403.2258064516129,
  406.5040650406504,
  406.5040650406504,
  409.8360655737705,
  409.8360655737705,
  409.8360655737705,
  409.8360655737705,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777,
  413.22314049586777
]

Now running the save AVG calculation on that

Like this .filter(v => v !== Infinity).reduce(function(acc, val) { return acc + val; }, 0)/100

The AVG pace of those samples is:

362.8961108433509

Which is not the same as converting the AVG SPEED to Pace

What can I be doing wrong? (Working on GAP)

[jimmykane]

Also on https://stackoverflow.com/questions/60529687/issue-with-avg-calculation-in-javascript

[jimmykane]

So the problem is more conceptual.

Speed [10, 0] = avg 5ms = 200s pace Pace [100, infinity] = avg 50s which is incorrect

[jimmykane]

One solution is to convert the pace to speed again (if not derived from speed already_ and do in that domain the avg calc

[jimmykane]

Closed via 92d77f0940ca269f23b9f8e41623cbdb28aaa4f3