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1. | linear equation | Yi,new = C 1Yi,old + C2X2,j + C3X3,k + C4X4,l + C5X5,m + C6 |
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2. | multiplication | Yi = X1,jX{~}2,kk~ |
3. | division | Yi = X1,j / X2,k |
4. | involution | Yi = X1,jX2,k |
5. | natural logarithm | Yi = ln(Xj) |
6. | common logarithm | Yi = 10 log(Xj) |
7. | exponential | Yi = exp(Xj) |
8. | power of 10 | Yi = 10Xj |
9. | power | Yi = XjC1{} |
10. | power of constant | Yi = C1Xj |
11. | polynomial | Yi = C0+C1X1,j + C2X1,j2 + C3X1,j3 + C4X1,j4 |
12. | conditional | Yi = max (X1,j, X2,k, X3,l, X4,m, C) |
13. | conditional | Yi = min (X1,j, X2,k, X3,l, X4,m, C) |
14. | conditional | Yi = mean (X1,j, X2,k, X3,l, X4,m ) |
15. | drift | Yi = X1 + C1dt + C0 |
16. | conditional | if Xi < C1 then Yi = C0 else Yi = Xi |
17. | conditional | if Xi > C1 then Yi = C0 else Yi = Xi |
18. | conditional | if Xi < C1 then Yi = C0 else Yi = Xi |
19. | conditional | if Xi = missing then Yi = C0 else Yi = Xi |
20. | conditional | if X1 = missing then Y = X2 2~ else Y = X1 1~ |
where:
Xp = equidistant time series p
Cp = coefficients
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Non-equidistant time series can be transformed into equidistant time series. The function computes the equidistant values in 2 steps. First it aggregates the non-equidistant time steps to equidistant time steps, when calculating the function makes a difference between accumulated parameters and instantaneous parameters. Generally, the non-equidistant series may not fill all equidistant time steps. You can select one of the following options to fill in the gaps:
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A special option is "Average over time step". This option uses a weighted average over the values in the next time step. In the previous example, the value for 01-01-2000 05:30 is 0.0033, this is the weighted average for all time steps between 05:00 and 05:30 ((15*-0.015 + 2*0.019 + 5*0.017 + 6*0.026 + 2*0.022)/30 = 0.0033). For filling the gaps the value of the next time step is used.
Example:
The underneath table shows the differences between the 4 options for filling in the gaps.
Original Series |
| Equidistant |
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| Zero | Missing | Linear | Equal Last | Average |
01-01-2000 00:15 | -0.049 | 01-01-2000 | -0.049 | -0.049 | -0.049 | -0.049 | -0.0495 |
01-01-2000 00:30 | -0.05 | 01-01-2000 00:30 | -0.05 | -0.05 | -0.05 | -0.05 | -0.0500 |
01-01-2000 00:45 | -0.05 | 01-01-2000 01:00 | 0 |
| -0.045 | -0.05 | -0.0405 |
01-01-2000 01:45 | -0.04 | 01-01-2000 01:30 | -0.04 | -0.04 | -0.04 | -0.04 | -0.0405 |
01-01-2000 02:00 | -0.041 | 01-01-2000 02:00 | -0.041 | -0.041 | -0.041 | -0.041 | 0.0033 |
01-01-2000 05:45 | -0.015 | 01-01-2000 02:30 | 0 |
| -0.03346 | -0.041 | 0.0033 |
01-01-2000 05:47 | 0.019 | 01-01-2000 03:00 | 0 |
| -0.02593 | -0.041 | 0.0033 |
01-01-2000 05:52 | 0.017 | 01-01-2000 03:30 | 0 |
| -0.01839 | -0.041 | 0.0033 |
01-01-2000 05:58 | 0.026 | 01-01-2000 04:00 | 0 |
| -0.01086 | -0.041 | 0.0033 |
01-01-2000 06:00 | 0.022 | 01-01-2000 04:30 | 0 |
| -0.00332 | -0.041 | 0.0033 |
01-01-2000 06:15 | 0 | 01-01-2000 05:00 | 0 |
| 0.004214 | -0.041 | 0.0033 |
01-01-2000 09:15 | -0.01 | 01-01-2000 05:30 | 0.01175 | 0.01175 | 0.01175 | 0.01175 | 0.0033 |
01-01-2000 09:30 | -0.013 | 01-01-2000 06:00 | 0.011 | 0.011 | 0.011 | 0.011 | 0.0000 |
01-01-2000 09:45 | -0.013 | 01-01-2000 06:30 | 0 |
| 0.0075 | 0.011 | -0.0115 |
01-01-2000 10:00 | -0.014 | 01-01-2000 07:00 | 0 |
| 0.004 | 0.011 | -0.0115 |
01-01-2000 10:15 | -0.008 | 01-01-2000 07:30 | 0 |
| 0.0005 | 0.011 | -0.0115 |
01-01-2000 10:30 | -0.009 | 01-01-2000 08:00 | 0 |
| -0.003 | 0.011 | -0.0115 |
01-01-2000 10:45 | -0.022 | 01-01-2000 08:30 | 0 |
| -0.0065 | 0.011 | -0.0115 |
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| 01-01-2000 09:00 | -0.01 | -0.01 | -0.01 | -0.01 | -0.0115 |
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| 01-01-2000 09:30 | -0.013 | -0.013 | -0.013 | -0.013 | -0.0135 |
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| 01-01-2000 10:00 | -0.011 | -0.011 | -0.011 | -0.011 | -0.0085 |
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| 01-01-2000 10:30 | -0.0155 | -0.0155 | -0.0155 | -0.0155 | -0.0220 |
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Errors may have an accumulative character, when the phenomenon causing the error has to do e.g. with siltation, weed growth, etc. hymosoffers the possibility to correct for this type of error by applying a continuously growing adjustment from the time the error is thought to have commenced till the error was detected and quantified. Let the error be DX observed at time t=i+k and assumed to have commenced k intervals before, then the applied correction reads:
X corr,j = X meas,j - ((j-i)/k)DX for ΔX for j = i, i+1, . ..., i+k
Input for this option are:
- series code,
- start and end date of the series correction
- error DX ΔX (mind the sign of the correction!)
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