In general, a trend is an observable pattern in the data.

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1answer
45 views

Statistically testing for a significant difference between two slope values [on hold]

I have five trend lines plotted in excel of number of prescriptions of a 5 different drugs over time (MM/YYYY) and I want to test the statistical significance of the difference between the slopes, to ...
0
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0answers
22 views

Detrending or Differencing in order to make a series stationary?

I got several time series for which I want to find out if they are stationary or not. So I computed for each series the kpss.test(). But before making further ...
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1answer
29 views

The constant term after 1st differencing

My instructor stated that when the dependent variable is 1st differenced, the constant term represents the deterministic change or trend in the dependent variable. When I search for information ...
0
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0answers
35 views

determinstic trend in VAR-models

I'm asking myself the following question. I want to build a VAR-Model with 6 time series A, B, C, D, E and F. I analysed every series univariate and I found out that A, D, E and F are stationary and B ...
0
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0answers
4 views

How to adjust rank for ad for its recent trend in click-through-rate?

I am building an optimization service for an Adtech company. For ranking ads in terms of performance, I am using formula: Log(impressions)*eCPM. Impressions means the number of times ad was ...
3
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0answers
37 views

Seasonal Kendall test and the Mann-Kendall test

I am trying to detect trends using non-parametric methods but I'm a little confused as to when you should apply the Seasonal Kendall test. Don't get me wrong I know you apply it when you have ...
0
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0answers
11 views

Can you compare groups over time if data has been collected at different time points?

If have two groups with follow-up measures of a normally-distributed continues outcome measure. One group is measured at 4 time points with unequal intervals. The other group is measured at 7 time ...
0
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1answer
31 views

Deterministic trend and noise

I have a chicken-egg problem in time series: How do we remove the deterministic trend in time series when you have a guess that the noise is non-normal? How do we check if the noise is non-normal ...
2
votes
1answer
77 views

markov chain with probability trends

I have clients with debts that can pass from states own 1 bill, own 2 bills, own 3 bills, leave the service, new debtors and owe nothing. So I could calculate the probabilities of being in state ...
0
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2answers
75 views

fitting a cubic polynomial to a trend component of time series

I have 295 observations of two variables, of which here are a few: ...
4
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2answers
173 views

Do you see trends in my residual plots?

Do you see trends in my residual plots? These residuals plot show the standardized residuals against fitted values, origin period, calendar period, and development period. The patterns in any ...
0
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1answer
21 views

How do I know if this jump is going against the downwards trend?

I'm looking at some accident statistics and have a question about how it's reasonable to interpret the data. The numbers are fatalities in traffic accidents, and I want to discuss a newspaper article ...
3
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1answer
58 views

Test for trend (ordinal predictor, continuous outcome)?

I have measured a continuous outcome variable in three groups of patients, where the groups are related to the severity of disease (control, mild disease, severe disease). I would like to test for a ...
3
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0answers
27 views

What is the ‘Pile-up Problem’?

In methods of trend-cycle decomposition, what is meant by the 'pile up problem'? How can the pile up problem be detected? Can it be detected by the method of visual inspection? If so, what are the ...
2
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1answer
50 views

Time Series Stationarity

I am confused of why my Dickey-Fuller test is significant (which implies stationarity), while the time series clearly exhibits a deterministic trend?
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0answers
30 views

Is smooth.spline appropriate for presenting the trend of chemical concentration in a catchment [closed]

In my case,the Electrical Conductivity (EC) values are measured daily in some pints of catchment from 2007 to 2014, and around 20% data are missed, due to without probe or flux. To presenting the ...
-3
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1answer
37 views

I am wondering what model to use [closed]

I am trying to do an analysis of popularity growth, in particular of the rate of growth in play count for artists on an online music streaming service. I want to create a postgresql db filled with ...
0
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0answers
19 views

Unit Root Confirmed- How generate the new series with Diff, Trend,Intercept

I have a data series that became stationary at first difference and including both Trend and Intercept. I know how to generate a new variable using first differencing (Eviews) but how should I cater ...
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0answers
16 views

Trend Survey Statistical Tests

I am designing a trend survey using a Likert style survey. I have three opinion questions, each with the same choice of responses ranging from Not Likely to Very Likely. Are there any statistical ...
0
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0answers
76 views

Single group with repeated measures using R? - Trend analysis (linear, quadratic effect)

I wonder how to get the repeated measures analysis of variance using R. My data is like this. ...
0
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0answers
8 views

Find Points that Break a mutli-valued Relationship

I am looking for a suggestion on how to answer a question, or what to read more about. I am sorry if I do not sound professional, I am not. First a contrived example. I have a table of 50 states in ...
0
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0answers
26 views

Infer significance (in trends) in time-series data

I got a dataset with multiple time variables (i.e. 21 fixed measurement times). It is expected that a (downward) trend over time can be discerned in these variables. When plotting scatterplots I find ...
2
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0answers
81 views

Detecting a trend to increase, in a time series, in real time

Probably, someone who's into technical analysis of share prices eats stuff like this for breakfast. Me, I couldn't devise a theoretically acceptable approach. I have this thing (private working set, ...
1
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2answers
36 views

Predict Seasonal Variations

I am developing an application related to pharmaceutical industry. Certain items are sold in significantly higher quantities during specific periods of the year. For example, here in my country, ...
1
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1answer
57 views

Can you identify what the sharp spikes in our data could be?

Scenario: There was an online competition to win a prize. The competitors are technology start-up companies and the prize is worth around 5,000 USD. There was a public, online vote to decide the ...
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0answers
85 views

STL-decomposition of a time series with deterministic trend and seasonality

what is the relationship between STL-decomposition and deterministic components of time series like trend or seasonality? I have a time series with deterministic trend and deterministic seasonality, ...
1
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1answer
168 views

What if the trend is changed?

I want to forecast tourist arrivals using time series analysis. I expected to use monthly data from 2000-2013. But due to the civil war, the trend was changed after 2008 as in the following plot. ...
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5answers
247 views

How to characterize abrupt change?

This question may be too basic. For a temporal trend of a data, I would like to find out the point where "abrupt" change happens. For example, in the first figure shown below, I would like to find out ...
1
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1answer
45 views

Rank deficiency in polynomial trend analysis

I am currently trying to fit a model for some reaction time data from an experiment with four consecutive blocks of the same task. I am interested whether there is something like an effect of practice ...
3
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1answer
29 views

Is there a method to disentangle multiple lines of data that are intermingled?

I have 3 temperature sensors that record data once a minute. All 3 temperatures have the tuple value (instant, temperature). The problem is, they may come in a random order and thus there's no way to ...
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0answers
13 views

Deviation from a trend- Help to define the problem

I am trying to define a problem I have in proper statistical terms. Here's what I have: I have a set of values measured monthly. These values are expected to grow pretty steadily over time. I need to ...
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0answers
29 views

Find linear subsets in a 2D point (xy) data [duplicate]

My problem is the very idea of how to start the analysis of 2D point patterns, specifically how to find linear trends within their spatial pattern. I have XY data points which are organized like in ...
0
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0answers
31 views

Temporal trends with missing values

I need to calculate the temporal trends for some climate variables with missing values. For example, last frost days defines as the last day of year with minimum temperature less than 0C. However, ...
2
votes
0answers
92 views

What is a “Wald test for trend?”

I am reviewing a manuscript and the authors state that some results are by a "Wald test for trend". Has anyone heard of this? I hadn't, and Google revealed nothing. I know I always say to provide ...
2
votes
1answer
56 views

Can I difference after fitting a time series regression model?

Suppose that I have a time series that exhibits a notable trend, and I want to test a hypothesis that a second variable is related to that trend. I fit a linear regression model with that second ...
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0answers
61 views

Trend: Linear or exponential

I am trying to forecast data using ARIMA. I have read articles which say that I should first take the log of the series, if my series follows an exponential trend. My question is: Is there a ...
0
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1answer
169 views

How to dampen forecast to improve accuracy?

According to Armstrong there is ample empirical evidence that dampening trends in uncertain and complex long term forecasting helps improve accuracy/reduce forecasting errors. What I'm not able to ...
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1answer
805 views

Difference between series with drift and series with trend

A series with drift can be modeled as $y_t = c + \phi y_{t-1} + \epsilon_t$ where $c$ is the drift(constant), and $\phi=1$ A series with trend can be modeled as $y_t = c + \delta t + \phi y_{t-1} + ...
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0answers
73 views

DLM Trigonometric seasonality vs trend

I am working with a structural time series model in R using dlm that has both a stochastic (slope and intercept) local trend and two trigonometric seasonal components (sin and cos pairs). I have ...
2
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0answers
216 views

Prewhitening time series: ARIMA-modelling versus polynomial trendelimination

I'm concerned with Box-Jenkins-models and especially the first step, the prewhitening to obtain meaningful crosscorrelations for identifying transfer functions and building regression models. I'm ...
0
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0answers
35 views

Trend estimation for participation?

I have logs for users and posts in a blog platform for 3 years. I can easily find out how many posts each user have made per day/month/year/etc. What I want to find out is if the frequency of posts ...
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2answers
102 views

Power calculation for a test of trend over time

This paper (open access) Babies born at the threshold of viability: changes in survival and workload over 20 years (table 2) presents data for survival of extremely premature babies over the last 20 ...
1
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1answer
81 views

How to find which time series is trending more?

Let us say I have two sets of time varying series as shown below: ...
2
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1answer
192 views

How to define weights when testing an exponential trend?

In a linear model including ANOVA one can test a trend (e.g., linearity, quadratic effect, etc.) among the ordered effects (regression coefficients or factor levels) through assigning proper weights. ...
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0answers
43 views

What is usefulness of time series decomposition if building a multivariate model?

I am at the early stages of building a panel regression model of sales data. I know my final model dataset will consist of log sales, control variables and log media variables. I am planning to use ...
5
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2answers
1k views

R detect increasing/decreasing trend of time series

I have lots of time series with periods: day, week or month. With stl() function or with loess(x ~ y) I can see how trends of ...
0
votes
1answer
271 views

Testing “trends over time” of dummy variables

Let us say this is an output of a model I ran in Stata, where int_retis a continuous variable and time1-...
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2answers
736 views

How to test for presence of trend in time series?

Apart from detecting trend from a time series plot, how do you test for its presence before removing the trend using moving average? I fitted a mathematical trend to the data and the slope was ...
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0answers
22 views

Measuring treatment effect on top-ranked subjects selected at point in time from longitudinal data

I am trying to measure the effect of treatment after some time on a group of subjects who were selected for treatment because they were the highest (top 1200) ranked subjects during a single period ...
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0answers
128 views

Trend and seasonality tests for a univariate time series

I am working with a batch of about 1000 univariate time series in R . For every time series, I have to perform following tasks , before deciding upon a model be it ARIMA, TAR or Holt Winter's Model ...