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From |
Sergiy Radyakin <[email protected]> |

To |
"[email protected]" <[email protected]> |

Subject |
Re: st: Recency Weighted cumulative exposures |

Date |
Thu, 14 Nov 2013 08:57:32 -0500 |

In this case your weight column as shown in the first post does not make sense. I am still not getting exactly the numbers you want as answers, but see if this brings you closer: do http://radyakin.org/statalist/2013111301/recencyw3.do +---------------------------------------------------------------------------------------------+ | csumstr csum result | |---------------------------------------------------------------------------------------------| | 1*0 0 0 | | 1*0+.9859553*0 0 0 | | 1*2.6+.9859553*0+.9449936*0 2.5999999 2.6 | | 1*2.6+.9859553*2.6+.9449936*0+.8804709*0 5.1634836 5.174 | | 1*3.2+.9859553*2.6+.9449936*2.6+.8804709*0+.7974722*0 8.2204671 8.218 | |---------------------------------------------------------------------------------------------| | 1*0 0 0 | | 1*0+.9859553*0 0 0 | | 1*.7+.9859553*0+.9449936*0 .69999999 .7 | | 1*.7+.9859553*.7+.9449936*0+.8804709*0 1.3901687 1.393 | |---------------------------------------------------------------------------------------------| | 1*0 0 0 | | 1*5+.9859553*0 5 3.511 | | 1*8+.9859553*5+.9449936*0 12.929776 9.891 | | 1*10+.9859553*8+.9449936*5+.8804709*0 22.61261 18.696 | | 1*8+.9859553*10+.9449936*8+.8804709*5+.7974722*0 29.821856 26.256 | | 1*5+.9859553*8+.9449936*10+.8804709*8+.7974722*5+.702151*0 33.368706 31.186 | | 1*10+.9859553*5+.9449936*8+.8804709*10+.7974722*8+.702151*5+.6009799*0 41.184967 41.186 | +---------------------------------------------------------------------------------------------+ If this is still not the algorithm you want, send me the spreadsheet. All your examples start with the first dose equal to zero. it is a bad illustration (even if it is true in you data) and does not help communicating what you want to be done. If you can't send the spreadsheet, run the following patients through it: A: 5.678 B: 1.234 2.345 C: 9.999 8.888 7.777 Show the results in the form of the csumstr above and without any letters anymore, so that one could -display- the result: . display 1*10+.9859553*5+.9449936*8+.8804709*10+.7974722*8+.702151*5+.6009799*0 41.184967 Take the example of 5.174 from your first post. The cumulative dose of 5.174 is w1*2.6+w2*2.6 right? w1 is 1, then w2 is 0.99 (exactly). Where is 0.99 coming from? is that .9859553 rounded? Best, Sergiy Radyakin On Thu, Nov 14, 2013 at 5:17 AM, Carmine Rossi, Mr <[email protected]> wrote: > Thank you again Mr. Radyakin and all STATA listers for your time. > > I will provide one more (fresh) numerical example, perhaps it would be more clear. It is for one id with 7 visits. "Result" is the variable I am looking to create. It is correct and follows the methods outlined in Abrahamowicz et al, and I am a student of his (2006, JCE, http://www.ncbi.nlm.nih.gov/pubmed/16549262). I used an excel spreadsheet to calculate the "result" variable, as I still am unable to program it in STATA, but this hand calculation method is tedious and impossible for large datasets (see all my calculations below). > > id time dose result > 1 1 0 0 > 1 2 5 5 > 1 3 8 12.930 > 1 4 10 22.613 > 1 5 8 29.822 > 1 6 5 33.369 > 1 7 10 41.186 > > To calculate the "result", which is a recency-weighted cumulative sum, the following calculations are made at every time point. > > The weight function, selected a priori is: exp((-((delta_t)^2))/(70.7)) > > > -------Hand Calculations begin--------- > > For time=1: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 0 1 0 0 [this is result shown at time==1] > > > For time=2: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 1 0.98595 0 0 > 1 2 5 0 1 5 5 [this is result shown at time==2] > > For time=3: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 2 0.9450 0 0 > 1 2 5 1 0.98595 4.930 4.930 > 1 3 8 0 1 8 12.930 [this is result shown at time==3] > > For time=4: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 3 0.8805 0 0 > 1 2 5 2 0.9450 4.725 4.725 > 1 3 8 1 0.98595 7.888 12.613 > 1 4 10 0 1 10 22.613 [this is result shown at time==4] > > For time=5: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 4 0.7975 0 0 > 1 2 5 3 0.8805 4.402 4.402 > 1 3 8 2 0.9450 7.560 11.962 > 1 4 10 1 0.98595 9.860 21.822 > 1 5 8 0 1 8 29.822 [this is result shown at time==5] > > For time=6: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 5 0.7022 0 0 > 1 2 5 4 0.7975 3.987 3.987 > 1 3 8 3 0.8805 7.044 11.031 > 1 4 10 2 0.9450 9.450 20.481 > 1 5 8 1 0.98595 7.888 28.369 > 1 6 5 0 1 5 33.369 [this is result shown at time==6] > > > For time=7: > > id time dose delta_t weight dose*weight cumulat_sum(dose*weight) > 1 1 0 6 0.6010 0 0 > 1 2 5 5 0.7022 3.511 3.511 > 1 3 8 4 0.7975 6.380 9.891 > 1 4 10 3 0.8805 8.805 18.696 > 1 5 8 2 0.9450 7.560 26.256 > 1 6 5 1 0.98595 4.930 31.186 > 1 7 10 0 1 10 41.186 [this is result shown at time==7] > > > -------Hand Calculations end--------- > > Notice how the weights are not fixed. They change depending on which time point you are calculating the recent cumulative sum. This is why I initially thought I needed to use a for values loop or something similar. > This is what I am trying to program, and so far, it has been very difficult. > > I want to thank you again for looking at this and giving it a shot. I appreciate it very much! > > Have a great day, > > Carmine Rossi > PhD Candidate, Epidemiology > [email protected] > > On 2013-11-13, at 11:42 PM, Sergiy Radyakin <[email protected]> > wrote: > >> On Wed, Nov 13, 2013 at 7:42 PM, Carmine Rossi, Mr >> <[email protected]> wrote: >>> Hi Mr. Radyakin, >>> >>> Thank you very much for your email and help. However, the code is not correct. >> >> Well it is pretty close to what you are looking for. The main >> difference is that 'delta time' was not defined in your formula, so I >> took absolute time, and you now describe relative time. That is also >> easily fixable: >> >> do http://radyakin.org/statalist/2013111301/recencyw2.do >> >> I am still NOT getting your exact numeric values, but it might be due >> to the rounding. Is your magic number 70 shown exactly? Is it same for >> all IDs? Are there any digits not shown for dosage? You may want to >> share your spreadsheet to reduce the traffic. >> >> Now I expect this modification to take care of both issues you >> mentioned since they essentially appear the same to me. Except I can't >> agree that the weights depend on the sum. I'd insist that the sum >> depends on the weights. The weights depend on the time. >> >> Best, Sergiy >> >>> >>> There are two issues: 1) The number of observations per ID is not constant, so for the macro `mt', it would need to be specific per id. For example, ID==1 has 5 time points, and ID==2 has 4 time points. >>> >>> 2) The weights are not fixed. This is more difficult for me to explain, but I will try. >>> >>> To get the "result" for ID==1 and time==5, I used the spreadsheet calculations shown in the previous email. >>> However, if I was to calculate the "result" at time==4, I would use the following weights: >>> >>> id time dose delta_t w(t) dose(t)*weight(t) cumulative_sum >>> 1 1 0 3 0.88 0 0 >>> 1 2 0 2 0.94 0 0 >>> 1 3 2.6 1 0.99 2.574 2.574 >>> 1 4 2.6 0 1 2.6 5.174 >>> >>> Notice how, now the weight, w(t), at time==4 is equal to 1, when I want to calculate the cumulative sum at time==4. >>> >>> For this reason, I thought I would need loops, and this is why I am asking the STATA community for help. My major issue is that the weight’s are not fixed and they change depending on the cumulative sum that I want to calculate at each time point. >>> >>> Thank you again for trying to help, >>> -Carmine Rossi >>> PhD Candidate, Epidemiology >>> [email protected] >>> >>> On 2013-11-13, at 5:23 PM, Sergiy Radyakin <[email protected]> wrote: >>> >>>> Carmine, no loops are really necessary: >>>> >>>> do http://radyakin.org/statalist/2013111301/recencyw.do >>>> >>>> Hope this helps, Sergiy Radyakin >>>> >>>> >>>> On Wed, Nov 13, 2013 at 5:08 PM, Carmine Rossi, Mr >>>> <[email protected]> wrote: >>>>> Dear STATA listers, >>>>> >>>>> I have the following repeated measures data on two subjects with a dose exposure variable. I am interested in creating a variable called “result” that is a recency-weighted cumulative sum. >>>>> >>>>> id time dose result >>>>> 1 1 0 0 >>>>> 1 2 0 0 >>>>> 1 3 2.6 2.6 >>>>> 1 4 2.6 5.174 >>>>> 1 5 3.2 8.218 >>>>> 2 1 0 0 >>>>> 2 2 0 0 >>>>> 2 3 0.7 0.7 >>>>> 2 4 0.7 1.393 >>>>> >>>>> The “result” variable is obtained as a cumulative sum using a weight function: >>>>> Summation of (Dose(i) x weight(t)), where the weight function is: >>>>> >>>>> W(t) = exp((-(delta time)2)/70.70) >>>>> >>>>> So to get the weighted cumulative sum value of 8.218 (for subject 1 at time 5), rather than 8.4, which would have been the un-weighted cumulative sum, I did the following in a spreadsheet. >>>>> >>>>> >>>>> Id time dose delta_t w(t) dose(t)*weight(t) cumulative_sum >>>>> 1 1 0 4 0.80 0 0 >>>>> 1 2 0 3 0.88 0 0 >>>>> 1 3 2.6 2 0.94 2.444 2.444 >>>>> 1 4 2.6 1 0.99 2.574 5.018 >>>>> 1 5 3.2 0 1 3.2 8.218 >>>>> >>>>> Is there a way to do this in STATA with loops? Can anyone provide any suggestions? >>>>> >>>>> >>>>> Carmine Rossi >>>>> PhD Candidate, Epidemiology >>>>> McGill University >>>>> [email protected] >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Recency Weighted cumulative exposures***From:*"Carmine Rossi, Mr" <[email protected]>

**Re: st: Recency Weighted cumulative exposures***From:*Sergiy Radyakin <[email protected]>

**Re: st: Recency Weighted cumulative exposures***From:*"Carmine Rossi, Mr" <[email protected]>

**Re: st: Recency Weighted cumulative exposures***From:*Sergiy Radyakin <[email protected]>

**Re: st: Recency Weighted cumulative exposures***From:*"Carmine Rossi, Mr" <[email protected]>

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