DOWNLOAD ZGRAPHER

The dataset must be in the format ". These are worked out by making a prediction for each step of the time series and trying to minimise the squared error for this prediction that is one step ahead. Where a T is the current trend level, b T is the current gradient of the trend and s T is the appropriate seasonal effect. This deseasonalised series is then smoothed using LOESS and this the the trend values that are used for the next loop through. We will be using NZgrapher to do the 'data crunching' to 1 - take a random sample, 2 - calculate sample statistics, 3 - produce a comparative box plot 4 - add informal confidence intervals to the box plots.

Uploader:	Goltiran
Date Added:	21 March 2009
File Size:	56.97 Mb
Operating Systems:	Windows NT/2000/XP/2003/2003/7/8/10 MacOS 10/X
Downloads:	48374
Price:	Free* [*Free Regsitration Required]

Nayland College - Mathematics Home.

Cleveland and others, and published in the Journal of Official Statistics in Because of the nature of exponential smoothing, the most recent values always have the greatest impact on the forecasts that we will make.

This is the interval within which we can be reasonably sure the actual population median occurs. Nayland College - Mathematics.

Please do not take a screenshot as it does not produce high quality plots to analyse. The sample is taken from the whole population, and we want to get at least 30 data values for each group, so zgrapehr sample of say 80 is needed.

How does NZGrapher Produce its Time Series Plots?

We will be using NZgrapher to do the 'data crunching' to 1 - take a random sample, 2 - calculate sample statistics, 3 - produce a comparative box plot 4 - add informal confidence intervals to the box plots. To do this these two boxes must be selected. For variable 2 the groups that are to be compared are selected.

The seasonal values are calculated by subtracting the series created in 3 from the series created in 2. STL is a method of decomposing historical data to analyse time series based on a long term trend and a seasonal component. If you click up here zgrqpher can select a built-in dataset. This is not something that students are expected to know or understand, but it is useful to be able to point in this direction for students who are wanting to really understand what is going on.

Once the loop is finished going through the required number of times, the zgrapber series from step 6 forms the trend blue lineand the seasonal values from step 4 form the seasonal value orange line. Once you have selected the graph you need to select the variables.

Where a T is the current trend level, b T is the current gradient of the trend and zgraher T is the appropriate seasonal effect. For variable 1 it must be numeric number-based as the message suggests.

MathsNZ Students - NZGrapher - Dataset Information

Apr 2, 8: Using the sample statistics from above, for each group you will need to find the informal confidence interval. These are what is known as exponential smoothing formula, and as you can see they have three extra variables: Subtract the trend from the raw data.

Do the intervals overlap? You can access the full article here.

The initial values for the seasonal effects are the difference between the first year values and the value of the linear trend line. NZGrapher uses the final values of a tb t and s t to make the main predictions shown by the solid red line on NZGrapher, and for the pink bands of expected values it does a bootstrap process times of what could happen from normal variation from what is seen in the data, and takes the middle of them to give the most likely outcomes.

If you click here you can upload or paste your own data set. The concept of using sample statistice to determine an estimate of the population is the key idea. Once it has done this it draws in the blue and green lines on the time series recomposition graph. Titles can be modified by typing in the boxes below the graph and then clicking the update graph button To copy the graph right click on the graph to select the image, and then either save or copy it into your document.

To start off with NZGrapher creates a centered moving mean for the first two years of data. Get all the values for each season eg: Once the data is loaded, select the graph type, and for this topic you select " Dot Plot and Box and Whisker".

Once it has done this it fits a linear trend to it. A deseasonalised series is then created by subtracting the seasonal values from 4 from the raw data. The Holt winters uses the following formulas to work out the values of a Tb T and s T as it goes through: The Holt-Winters model requires a number of values to be chosen, the first few are the initial values for the trend, the gradient of the trend and the seasonal effects.