Latest Contributions by LaurenRosenshein

‎02-28-2011

Hi Todd, Sorry to hear that you are having trouble with your analysis! In order to figure out what is going on here, we need a bit more information. If possible, could you send us your data and we can try to repro it? If that isn't possible, can you send us some screenshots of your attribute table and the tool dialog right before you run it? Again, sorry for the inconvenience! Hopefully we can get you up and running again soon! Lauren Rosenshein Geoprocessing Product Engineer

‎02-28-2011

Hi Michelle, Sorry that you are having trouble generating a Spatial Weights Matrix!! I have a couple of suggestions that may help. One suggestion is to try creating a new field of type Long, and calculate the field using the FID/OID. Then, and this is important, shut down ArcMap, then reopen it and try to use that new field you created. You may be having trouble with a bug that was fixed at 10.0 SP1 that involves empty selections after new fields are calculated. Closing down ArcMap seems to do the trick. And if you haven't installed 10.0 SP1 yet, I strongly encourage you to do that as well. Another possibility is that the field that you are trying to use does not contain unique values? The Unique ID has to have a different value for each feature, which is why we suggest using either the FID or the OID for calculating your new UniqID field...just in case. Sorry for the inconvenience! Lauren Rosenshein Geoprocessing Product Engineer

‎02-28-2011

Hi Carrie, Glad to hear that you're interested in learning more about Hot Spot Analysis! My suggestion would be to use the Hot Spot Analysis Tutorial. Even though the tutorial is designed for 9.3/9.3.1 is should still provide you some valuable step-by-step instructions for 9.2. You may also find the videos and other resources at our Spatial Statistics Resources Page helpful! You can also get to the page from the easy-to-remember URL: http://esriurl.com/spatialstats. From there we have links to lots of instructional videos, free training seminars, and a ton of other stuff. I would definitely suggest starting with the 3 short videos on Hot Spot analysis. Actually, we just did a Live Training Seminar which was an Introduction to Spatial Pattern Analysis, and that probably has a lot of useful information as well. It is all done in 10.0, but all of those tools (and the associated workflows) are still relevant for 9.2. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎02-28-2011

Hi Josef, That's a great question! You absolutely can trust the results of your Hot Spot Analysis (Getis-Ord Gi*) on data with negative values. The Getis-Ord Gi* statistic that is implemented in ArcGIS is based on the 1995 paper by Getis and Ord (Ord, J.K. and Arthur Getis. 1995. "Local Spatial Autocorrelation Statistics." _Geographical Analysis_ 27(4): 287-306.). The 1995 implementation absolutely DOES allow for negative values, so you can go ahead and feel confident in the results that you're getting. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎01-12-2011

Hi Molly, Thanks for your question, it is a really good one! You are right that just looking at the z-scores for your features is not enough to determine with what COType that feature will be classified. For instance, a strong, negative z-score that is statistically significant is always an outlier, but whether it is classified as HL or LH is based on more information than just the z-score. And the same can be said for strong, positive z-scores and HH and LL classifications. For each feature in the dataset we calculate the z-score, p-value, and local mean, and then for those features that are statistically significant we go on to determine the classifications. The global mean is the average of all of the analysis field values; the local mean is the average analysis field value for a target feature�??s neighbors. For outliers (strong, negative z-scores <-1.96) we compare the value of the target feature to the local mean. So, those features with values that are higher than the local mean are classified as HL, and those features with values that are lower than the local mean are classified as LH. For clusters of similar values (strong, positive z-scores >1.96) we compare the local mean to the global mean. Those features with local means that are higher than the global mean are classified as HH, and those with local means that are lower than the global mean as LL. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎01-05-2011

Hi Eve, I'm glad to hear you got GWR working! As far as the creation of a spatial lag variable, at this time we have not implemented this functionality in the Spatial Statistics toolbox. We have been working on a Sample Script (for the Geoprocessing Resource Center) that would create a spatial lag variable using R from within ArcGIS, but we are busy with 10.1 development and it may be a little while before that happens. If you are familiar with R, you may find this existing sample script useful as a template for leveraging R (the same way we are planning to in order to create spatial lag variables in the future). You may also find this link valuable for additional resources on spatial statistics: http://bit.ly/spatialstats Lauren

‎01-04-2011

Hi Paula, I'm glad to hear that the resources are helpful! You can find the step-by-step model creation in the Hot Spot Analysis Tutorial. Hope this helps! Lauren

‎01-04-2011

Hi Eve, I'm sorry to hear that you are having trouble running GWR on your dataset, and hopefully we can figure it out and get you moving forward quickly! You should not be having trouble running GWR on a dataset with 27,000 points. I just tried to reproduce the problem with a dataset with 30,000 points in 10 sp1 and had no trouble. So, let's try to figure out what is going on. In order to move forward, can you please provide the following information: --What version of ArcGIS are you using? --What do you mean by "no results"? Are the results being created but not added to your table of contents? Are they not being created at all? Are they being saved to a valid path? --What are the exact steps that you are taking when you run your analysis? --Can you provide a screenshot of the Messages Window once GWR has executed sucessfully? Make sure that you run your analysis in the foreground if you want the messages window to appear when you are running GWR. Alternatively, you can right-click on the Messages from the Results window and choose to open them after the fact. Again, I am very sorry that you are having trouble and I'm looking forward to working with you to get the problem resolved. Lauren Rosenshein Geoprocessing Product Engineer

‎01-04-2011

Hi Clint, This is a great question! Actually, we've got a great sample script that shows using R from inside of ArcGIS to do cluster analysis! The sample script has several options for the cluster method, including cmeans, which may be just what you're looking for! 🙂 Even if it isn't the same method that you are currently using, the sample shows the use of python scripting within ArcGIS to connect to R. It may be a useful template for you moving forward so that you can avoid jumping in and out of ArcGIS and R. Additionally, we are currently working on an implementation of K-Means ++ Clustering, with optional space/time constraints. We're calling it Group Similar Features, and it will be in the Spatial Statistics toolbox in ArcGIS 10.1. I know that 10.1 is still a ways off, but we're really excited about it and hopefully you will find it valuable in the future. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎12-16-2010

Hi Andrew, This is a great question, and one that we get quite a bit. With GWR, there is a local linear equation for each feature in the dataset. The equation is weighted so that nearby features have a larger influence on the prediction of yi than features that are farther away. I do know that our consultant�??s GWR software (Fotheringham, Charlton and Martin) does compute p-values for each coefficient in every one of the local linear equations. However, because doing so is really not appropriate (and we�??ve discussed this with our consultants and they agree with that assessment), we do not report the coefficient p-values for our ArcGIS GWR tool. I know our consultants are looking into other methods for computing those p-values that might be appropriate, but I don�??t believe they have come up with an ideal solution. Because GWR does not have the strong diagnostics (like p-values, as just one example) that OLS does, we very strongly recommend finding a properly specified OLS model before moving to GWR. Unless you are only interested in predictions (not interested in the coefficients�?� in variable relationships), you cannot trust GWR results unless you can be sure you�??ve found all of the key explanatory variables to model your dependent variable (you can see this easily: run OLS or GWR with 1 important explanatory variable and examine the coefficients; add a second important explanatory variable and notice that the coefficient values change�?� sometimes dramatically; the coefficient values can change 180 degrees, in fact). Having said that, we have just released a tool and documentation on the Geoprocessing Resource Center to help you find a properly specified OLS model: Exploratory Regression and �??What they don�??t tell you about regression analysis�?�. The Exploratory Regression tool is similar to Stepwise Regression except instead of just looking for high Adj R2 values, it looks for models that meet all of the assumptions of the OLS method (no variable redundancy, no spatial autocorrelation in regression residuals, no model bias, statistically significant coefficients�?�). To download this tool and the associated documentation, check out http://bit.ly/spatialstats (look for Supplementary Spatial Statistics). Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎12-15-2010

Hi Paula, It's great to hear that you are interested in learning more about some of the spatial statistics tools in ArcGIS! We have a ton of resources that I think will be very helpful to you as you start learning about the tools and how they can help you analyze your data. To start with, it sounds like Hot Spot Analysis should work really well for the questions that you are trying to answer, as well as some other spatial statistics tools. We have all of our resources listed at http://bit.ly/spatialstats, including tutorials, short videos, hour-long free training seminars, and a lot more. The Hot Spot Analysis Tutorial and the Spatial Pattern Analysis Tutorial will be great places for you to start. They come with data, and walk you step-by-step through the analysis process. As far as Hierarchical Nearest Neighbor clustering, ArcGIS doesn�??t have that tool (we found results are very dependent on the first cluster found). I think Hot Spot Analysis will provide you with the results that you are looking for. However, if you feel that Hierarchical Clustering is an important solution to your problem, you may want to check out CrimeStat, which does include it in their package. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer

‎12-15-2010

Hi Paula, Even though your point data does not have an attribute associated with it that you would like to analyze, there are some techniques that you can use that will allow you to use the spatial statistics tools to run a hot spot analysis. We have a great tutorial that you can download that will walk you through a hot spot analysis of 911 calls. It should be very helpful because it walks through the workflow of aggregating the point data for use in tools that require a value field. You might also find this video useful as it describes the importance of thinking through parameters like the search radius. There are also a ton of additional spatial statistics resources available at http://bit.ly/spatialstats. Hope this helps. Lauren Rosenshein Geoprocessing Product Engineer

‎11-30-2010

Hi Steve, I am very sorry to hear that you are having trouble! We do everything that we can to ensure that users never get 999999 errors, so that sounds like a bug, and I am hoping that we will be able to figure out what is going wrong and fix it as soon as possible. There are a few things that I'll need to know in order to reproduce the issue, and ultimately fix the problem. What version of ArcGIS are you working on? Is it possible for you to share your data so that we can reproduce your exact workflow, and what are the precise steps that you are taking in your analysis (i.e. all of the parameter choices, inputs, etc.)? If you can share your data, you can send it to me directly at [email protected]. Again, I am very sorry for the trouble this has caused you! Lauren Rosenshein Geoprocessing Product Engineer

‎11-23-2010

That is a great question, Bill! So great, in fact, that I had to go ask a colleague down the hall. 🙂 The response that I got is as follows: A given point can move up to 1.4 X the cluster tolerance, but it�??s an iterative process, so the movement of a point, could move it within the cluster tolerance of other points, and shift it further. I think in this case, yes, all the points will shift, and will shift to the center of the grouping (2.5, 0). My colleague also pointed me to the help topic, Topology in ArcGIS, which I think you will find provides a lot of additional information on cluster tolerances. Hope this helps! Lauren

‎11-22-2010

Hi Bin, Another option for this type of grouping is to start with the Integrate tool (Data Management), which allows you to snap features together that are within a specified distance of each other. The integrate tool will change the coordinates of all input features so that those features within a specified distance of each other will be coincident. Please note that the Integrate tool will change your input feature class, so it is always a good idea to run Copy Features beforehand to ensure that you do not lose your original data. Once you have run Integrate, you can use the Collect Events tool from the Spatial Statistics toolbox to create a count of the number of coincident points at each location. This workflow is detailed in the Hot Spot Analysis Tutorial as a way to aggregate incident data for a hot spot analysis. The tutorial provides step-by-step instructions on creating a model to Integrate and then Collect Events using point data. Hope this helps! Lauren Rosenshein Geoprocessing Product Engineer Check out the latest Spatial Statistics resources at http://bit.ly/spatialstats!

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My Ideas

Latest Contributions by LaurenRosenshein

Re: Invalid Parameters Error 000581

Re: Trouble with Generating Spatial Weights Matrix

Re: hot spot analysis of 911 calls on map center

Re: hot spot analysis - variables with positive and negative values

Re: Local Moran's I: Computing "COtype"

Re: GWR data set limit

Re: How to perform Cluster and hotspot analysis?!

Re: GWR data set limit

Re: fuzzy c-means cluster analysis

Re: Mapping Geographically weighted regression, p values

Re: How to perform Cluster and hotspot analysis?!

Re: Cluster Analysis - geographic only

Re: ERROR 999999: Error executing function. A locator with this name does not exist

Re: How to create centroid of points within a certain radius?

Re: How to create centroid of points within a certain radius?

Re: Relationship between Getis Ord G* statistic an...