Speaker | Transcript |
| This talk is to highlight some |
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| time series platforms. Three are |
| from time series platforms and |
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| do we need Box Cox |
| transformed time series? |
| Let's take a look at the data |
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| also known as a as an airline |
| passenger data set. |
| The original series is |
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| model from. |
| Why? Let's take a look at a plot... |
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| getting larger. And this series |
| cannot be handled by the |
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| in the second picture. So the |
| variation does not change |
| with the various times series ??? |
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| So in the literature people will |
| say, well, we will transform |
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| of the transform scale, in this case |
| here, it's the log scale. |
| Sending it to inverse |
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| transform. |
| In the past...in the past |
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| streamline the whole process. |
| What you need to do is to put |
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| need to do the models, make |
| forecast, then the software, |
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| will put log passengers into Y, |
| but now we don't have to. We |
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| to enter the Box Cox |
| transformation parameter Lambda. |
| Zero, it means it's a log |
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| the red triangle menu and click |
| either ARIMA or seasonal ARIMA. |
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| 12 for seasonal part. |
| Without intercept. Click |
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| forecast taking care of the |
| inverse transformation. The |
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| will will show in this. |
| plot and the forecast had |
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| models is a workhorse in time |
| series forecast platform. |
| They can fit and forecast a lot |
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| performance is somehow comparable |
| to the forecasting |
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| study why it...why this type |
| of model works and why some some |
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| type model into the time series |
| platform which is designed to |
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| a function of the unknown |
| state, unobserved state. Here at |
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| variables and the error term |
| by either additive operations |
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| state is the level state time |
| series. Trend state forms a |
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| state, and also one of the |
| previous seasonal states. And |
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| previous trend state will |
| tremd to the next. |
| trend state and the level state |
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| point to another time point. And |
| there are more arrows...that there |
| are more states transitions than is |
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| series into Y and click OK. |
| To fit this type of model, we |
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| set, I'm going to enter 12 |
| for period. |
| And I'm going to click Select |
| Recommended button. |
| From the additive error models and |
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| this particular set, I'm going |
| to click constraint parameters |
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| recommended models to fit these |
| type of...these time series and |
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| model with smaller AIC and |
| my eyes are on the first two |
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| models. And let me |
| overlay the forecast |
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| from the original time series |
| more nicely. |
| So in my preference, I would |
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| difference? Let me open the |
| first one MAA...MAM. |
| Let's go down below. This |
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this one | component states. |
| This is a special for this |
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| the first letter. |
| And the trend is additive by |
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| second part of this report are |
| the...are the state component |
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| part is the prediction of |
| this specific state. |
| The period of the time series |
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| has an increasing pattern in |
| the past. It keeps increasing |
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| series and the pattern continues |
| toward the future, and this |
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| observed, but the forecast is |
| flat. This bothered me. |
| Now let's look at second |
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| state component graph. Level is |
| increasing in the past had |
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| future. This is more reasonable |
| plot that I can accept. So is it |
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| on to the second slide. |
| This slide and then the next |
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| on interpreting the forecasts |
| from from this model...this type of |
| models. Here I would like |
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| up. I listed half of them here. |
| Oh, nearly half. So let's focus |
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| some increase trend and will |
| taper off towards the end. |
| And on the other hand, we can |
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| see from the forecast using this |
| type model. If seasonality |
| is not involved. When I |
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| the first one, this is |
| a flat forecast if the seasonality |
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| have a linear increase |
| patern and so on so forth |
| similar to the others. Now |
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| it's merely increasing. |
| After applying the |
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| the multiplicative seasonality on |
| the top of our increasing |
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| this type...different type of |
shapes | flat |
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| we get those different...different |
| shapes. So I I re entering ??? |
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| what we eventually see in |
| the forecast. |
| You have the flat patterns or |
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| parameters. So I separated |
| these parts and also I |
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| trend will usually look flat, |
| we will get an increase |
| pattern in the level state. |
| When it's linear and |
| when it's curved. |
| It's all depends on how this |
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| increasing or decreasing in the |
| level exponentially. So this is |
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| is lean and think of it as |
| compound interest rate if |
| if the level state increase |
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| they make forecasts, they try to... |
| try not to overshoot |
| or undershoot the forecast that |
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| how to interpret |
| the forecast from state |
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| second one, none of of these |
| models are stationary. They are |
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| So if you are considering these |
| time series. Things |
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| third one, if you just see |
| that time series not |
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| a result in a...in |
| the next slide that will fit |
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| compare across type of |
| model be careful. |
| This slide is to show how... |
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| is the forecast. |
| And similarly, I plot my |
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| apply these type of state space |
| smoothing models to stationary |
| time series? Here I simulate a |
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| models to this time series, the |
| best model turns out to be in an |
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| rather different becauses it is |
| a random walk model and the |
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| feature in this presentation |
| forecast on holdback. |
| This feature allows you |
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| one is from another model. |
| And then you can compare these |
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| to activate this feature. Then I |
| need to specify |
| the length of the holdback |
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| click Select Recommended, |
| and check Constraint |
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| portion of the series, |
| we listed the holdback |
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| by default, but you can |
| always change the metrics you |
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| reports are similar to |
| to that got from the analysis |
| results without activating this |
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| let's let's let me summarize |
| what we have learned from |
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| performance over the holdback |
| data. But those criterias are |
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| process. We see the rather |
| different from how we use |
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| part of the model fitting |
| process, so this is something |
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| holdback to evaluate |
| different models based on their |
| forecasting performance. So we |
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| column is that time series |
| indicator. Y is time series |
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| summarize the data set, either |
| time or time series, by |
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| specification or change the |
| model selection strategy, we |
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| check...change selection in the |
| first combo box to forecasting |
| performance. Then we can choose |
| forecasting performance |
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| we want forecast. But you can |
| choose any...change to any |
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| using the training |
| time series, select the best |
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| series platform. First analyze |
| Box Cox Transformed time series. |
| The second one is fit state |
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| as well and using it as |
| And model selection method. |
| Thank you very much. |