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

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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
25 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 ...
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42 views

How to find which time series is trending more?

Let us say I have two sets of time varying series as shown below: ...
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1answer
89 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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12 views

Detecting poaching by age class proportion - suggested test for detecting decrease in given age class?

My dataset consists of observations of individuals, recording the date and the individual's age class. Age classes vary in bin size: 0-4 5-9 10-19 20-40 Example ...
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27 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 ...
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2answers
195 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 ...
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1answer
98 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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32 views

Multiple time series methods for trend identification, forecasting etc

I have several time series consisting of aggregated macro-economic indices and I am trying to choose one or several appropriate techniques in order to answer a number of questions. First, I need to ...
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2answers
150 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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25 views

How to test if the mean of data collected over many days is significantly higher on a predicted day

I have some data examining blog posts on different days. Basically, about 2000 news articles pertaining a certain topic were sampled and each blog post was given a positivity percentage score ...
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16 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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39 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 ...
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1answer
86 views

Trend test on historical stock prices, where to start?

I am a beginner on statistic but come across an urgent situation that I have to work with statistics of stock prices data. I have learned that ones can do a hypothesis test that rejects the Random ...
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19 views

Seasonal Data with Yearly “Step” Trend

Trying to plan for upcoming inventory needs for a clothing company. There is a strong seasonal component to the data. At the beginning of the year, sales are up; at the end, sales are down. Each ...
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64 views

Forecasting time series with trend and seasonality

I have a univariate time series, which has a trend and month seasonality. Traditionally I have been using auto.arima() method in R to model such series. So when I ...
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1answer
101 views

Pros and Cons: Methods for Detrending Time Series Data

My memory is fuzzy on the advantages and disadvantages of various methods for detrending time-series data. I'm looking for a succinct summary of why and when one should or should not use the ...
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1answer
63 views

Power of Seasonal Kendall Trend test

I was asked about doing a power analysis of a seasonal kendall trend test. I feel like that would be really difficult to do and I haven't found any documentation or software on how to do it. Is there ...
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1answer
165 views

ARIMA with difficult seasonality in R

I have non-stationary time series. It has evident trend in means and seasonality. These raw data are measured every second. On the plot of original series I see trend and seasonality about 80,81 ...
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3answers
159 views

R - Find curve pattern of simple time series

I have time series data of credit card transaction volumes for different companies. For example: week1: \$5000 week2: \$6000 week3: \$6200 week4: \$7000 week5: \$9000 ... Is there a simple method in ...
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49 views

How to perform a trend test

I'am working on a glm model (family:normal, link:identity) using complex survey design (package: survey), My interest is to evaluate the effect of the variable DLA on the scores. I ran the model 1 ...
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3answers
72 views

Basic question regarding n of 1 study. Four weeks intervention

I initially will apologise for any lack of clarity with regards to this question. I'm posing this on behalf of my sibling who is in the biomedical sciences. They have done an intervention on a ...
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3answers
126 views

Question about eliminating seasonality

I am trying to remove seasonality from data. I tried the non-linear trend using the code: trend=lm(NH3cH6~t+cos.t+sin.t). The plot was shown as following: However, as you can see, the second peak of ...
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34 views

Imputing missing values in a count time series with variable effort with the goal of trend estimation

I have a time series monitoring data set that looks like below: The response is a count. ...
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3answers
138 views

Deterministic components in covariates/exogenous variables in time series models

Actually, I have read a pair of books about time series analysis, but I am still not sure about how to treat deterministic components, like trend and seasonality, in the exogenous variables in a time ...
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2answers
202 views

Autocorrelation and trends

What is the relation between the autocorrelation and the trend? Can a trend exist in a time series of independent variables? And in time series with a non-zero autocorrelation, does a trend always ...
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1answer
109 views

Creating alert system based on standard deviation and mean: How to deal with small sample size, trends and seasonality?

I'm trying to build a daily alert system to let me know when something unusual has happened in my analytics data that might require further investigation. Right now I'm taking 7 weeks worth of data, ...
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2answers
786 views

Getting a second-order polynomial trend line from a set of data

Alright, so I have about a thousand datapoints that I'm plotting on a chart (scatter plot). Here's a few of the records: ...
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1answer
94 views

$R^2$ from a regression of two trend-stationary processes, $Y_t$ and $X_t$

In Estimation and Inference in Econometrics, by Davidson and MacKinnon, p.671, they claim that $R^2$ from a regression of $Y_t$ on $X_t$, where both time series are trend stationary, tends to 1 as $n$ ...
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1answer
365 views

When is it necessary to include the lag of the dependent variable in a regression model and which lag?

The data we want to use as dependent variable looks like this (it is count data). We fear that since it has a cyclic component and trend structure the regression turns out to be biased somehow. We ...
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3answers
175 views

how to robustly identify a floor trendline ignoring outliers?

I've got the following sets of data (x and y scales on each chart are identical): The eye picks out an upward-sloping floor trendline on each chart that runs upward from left to right, hugging the ...
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64 views

Valid way to highlight trends in growing data set

I have a summer research project that I'm currently working on that involves face recognition during a video capture session. I currently have an algorithm that returns a ranking of the closest ...
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75 views

How to account for short-term trends of time-series data?

I would like to find out which of my 10 independent variables (IVs) best accounts for the changes of my dependent variable at different points of time within the last 30 years. In order to explain ...
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83 views

Trend test for ratios

I have binomial data infected/not-infected on individuals of a sample from different years for two different infections. I have used prop.trend.test to test for ...
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2answers
107 views

Can time series be used to predict series which has a changing trend?

Supposing I have a stock return series from 2000-2013. Looking at the data, it has pattern of long trending bull market: 2001-2008, and 2010-2013, while it also has great reversal in 2008 financial ...
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1answer
648 views

Structuring a linear mixed model in R with nesting

My ecological question is: "What are the trends in percent coral cover by island and depth across the state of Hawaii from 1999 to 2012?" I am trying to analyze this hierarchical data set using R ...
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221 views

Test for linear trend in ANOVA

There is a webpage about linear trend test in ANOVA. The trend analysis procedures are designed to help assess whether there is a functional relationship between the IV and the DV. .... To ...
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16 views

What's the difference between expected frame and observed frame?

I'm working on detecting bursty keywords in a data stream. I read this question that does the same: Chi-squared test for detecting trending terms however I don't understand what's by "expected ...
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98 views

Detecting trends in a data stream in real-time

I'm trying to detect trending topics on Twitter in real-time. What I'm doing is every time I get a tweet I assign the tweet to the cluster that talks about the same topic as the tweet. Regardless of ...
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30 views

Identifying a trend in binomial experiments

I have a survey running each month that's answered each time by a random set of people. I want to investigate the trend in a particular set of questions to see whether opinions are changing over time. ...
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84 views

Statistical significance of long term trend?

I have data sets of long term climatology wind speed data on daily basis for 1950-2000. I have calculated the mean for every year and calculated trend pattern, it shows some positive trend of 0.05 ...
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27 views

Accounting for trend using complete block design

I would like to use ANOVA to compare the population means for several data samples consisting of the concentrations of a groundwater contaminant obtained from several groundwater monitoring wells. ...
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153 views

What is the difference between a stochastic and a deterministic trend?

Models with stochastic trends i.e., structural time series models are useful in some instances. Firstly, it may be hard to identify multiple structural breaks in the deterministic trend when the ...
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1answer
89 views

How to compare differences between groups, when measured values have decreasing trend

I'm currently performing challenging analysis and I'm not sure how to continue. I have three separate groups which had different procedures. In each of them there are four measurements (subjects were ...
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1answer
350 views

Detecting a (statistically) significant change in time series trend

Suppose I have two time series (Series1 and Series2) which are identical from timePeriod -200 to timePeriod 0. Say that in timePeriod 0 they are both equal to 100. Series1is equal to 200 at timePeriod ...
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840 views

Testing two trendlines for statistical significance

Background I am comparing data on how ATPase activity from flight and leg muscle from locusts reacts to different concentrations of calcium. I plotted a scatter graph of each data set on the same ...
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119 views

A measure of concordance

I have two data series same length = 80 points such as this picture My questions: How to compare overall trends? How to measure the concordance between swings? For swing I mean each line segment, ...
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1answer
82 views

Methods For Estimating Trend in R [closed]

Do you know how i can get a code for estimating trend by Mitcherlich and logistic method in R?
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125 views

Time-series autocorrelations all positive

I've got 36 months of timeseries data, and eyeballing it, it has a linear trend upward. I wanted to do a little more than just eyeball it though. So I put together a correlogram of autocorrelation ...
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1answer
165 views

Trend in data - determining according to angle between regression line and vertical line?

This question is a little bit referring to this question How to determine trend strength from linear regression slope? but I found a another solution so I am creating new question to confirm my idea. ...