Posts Tagged ‘ Data Analysis ’

The distribution of nearest neighbor distances

September 19, 2016
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The distribution of nearest neighbor distances

Last week I showed how to compute nearest-neighbor distances for a set of numerical observations. Nearest-neighbor distances are used in many statistical computations, including the analysis of spatial point patterns. This article describes how the distribution of nearest-neighbor distances can help you determine whether spatial data are uniformly distributed or […] The post The distribution of nearest neighbor distances appeared first on The DO Loop.

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Compute nearest neighbors in SAS

September 14, 2016
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Compute nearest neighbors in SAS

Finding nearest neighbors is an important step in many statistical computations such as local regression, clustering, and the analysis of spatial point patterns. Several SAS procedures find nearest neighbors as part of an analysis, including PROC LOESS, PROC CLUSTER, PROC MODECLUS, and PROC SPP. This article shows how to find […] The post Compute nearest neighbors in SAS appeared first on The DO Loop.

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Graph a step function in SAS

September 6, 2016
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Graph a step function in SAS

Last week I wrote about how to compute sample quantiles and weighted quantiles in SAS. As part of that article, I needed to draw some step functions. Recall that a step function is a piecewise constant function that jumps by a certain amount at a finite number of points. Graph […] The post Graph a step function in SAS appeared first on The DO Loop.

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Weighted percentiles

August 29, 2016
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Weighted percentiles

Many univariate descriptive statistics are intuitive. However, weighted statistic are less intuitive. A weight variable changes the computation of a statistic by giving more weight to some observations than to others. This article shows how to compute and visualize weighted percentiles, also known as a weighted quantiles, as computed by […] The post Weighted percentiles appeared first on The DO Loop.

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Formats for p-values and odds ratios in SAS

August 15, 2016
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Formats for p-values and odds ratios in SAS

Last week I showed some features of SAS formats, including the fact that you can use formats to bin a continuous variable without creating a new variable in the DATA step. During the discussion I mentioned that it can be confusing to look at the output of a formatted variable […] The post Formats for p-values and odds ratios in SAS appeared first on The DO Loop.

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Compute highest density regions in SAS

August 1, 2016
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Compute highest density regions in SAS

In a scatter plot, the regions where observations are packed tightly are areas of high density. A contour plot or heat map of a bivariate kernel density estimate (KDE) is one way to visualize regions of high density. A SAS customer asked whether it is possible to use SAS to […] The post Compute highest density regions in SAS appeared first on The DO Loop.

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What happened when I was forced to wait 30 minutes for the subway

July 18, 2016
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What happened when I was forced to wait 30 minutes for the subway: pondering how easy it is for data analysts to get fooled by bad data

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How much do New Yorkers tip taxi drivers?

May 2, 2016
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How much do New Yorkers tip taxi drivers?

When I read Robert Allison's article about the cost of a taxi ride in New York City, I was struck by the scatter plot (shown at right; click to enlarge) that plots the tip amount against the total bill for 12 million taxi rides. The graph clearly reveals diagonal and […] The post How much do New Yorkers tip taxi drivers? appeared first on The DO Loop.

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Visualize missing data in SAS

April 20, 2016
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Visualize missing data in SAS

You can visualize missing data. It sounds like an oxymoron, but it is true. How can you draw graphs of something that is missing? In a previous article, I showed how you can use PROC MI in SAS/STAT software to create a table that shows patterns of missing data in […] The post Visualize missing data in SAS appeared first on The DO Loop.

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Examine patterns of missing data in SAS

April 18, 2016
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Examine patterns of missing data in SAS

Missing data can be informative. Sometimes missing values in one variable are related to missing values in another variable. Other times missing values in one variable are independent of missing values in other variables. As part of the exploratory phase of data analysis, you should investigate whether there are patterns […] The post Examine patterns of missing data in SAS appeared first on The DO Loop.

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