Latest Contributions by DavidBirkigt

Scott, I have heard nothing on this topic, other than it is on the roadmap. So afaik still no private data, and no date for private data. ... View more

Thanks, I missed that in the help thread (probably stared at it for too long) Perfect answer David ... View more

Hi, To address your projection issue I can not give you a straight answer as I know nothing about picking a projection for big areas of the amazon, but this is essentially your problem. Your data is in a Geographic Coordinate System this system essentially describes the location of a place on a sphere in degrees (latitude longitude) and it just does not make sense to do any analysis on this as the degrees are not a uniform measurement (1 deg at the equator covers more distance then one deg at the north pole). That is where projections come in they are a mathematical way to transform the GCS onto a flat surface. But just like peeling an orange you cannot do this without distorting measurements, including distance, shape, area and angles. That is why there are so many different projections, they are useful for different things. I usually work in a single UTM zone, but you are working on the whole amazon which spans many UTM zones ao that is not the answer. I think in the end you will just need to do some research and find a projection that distorts the variable of concern (distance) the least for your study area, but whatever the solution is I doubt it will be perfect. You can check out this book, some parts are pretty technical but other parts are not, I think it is good, Datums and map projections for remote sensing, GIS, and surveying  By Jonathan Iliffe For as to why your data does not change projections when you try, you might want to read up on on the fly projecting in arcgis. What I usually do is go; view data frame properties and set the projection I want. Then export a copy of my files in this projection, open a new map (clears the projection) then add my projected data. There are a lot of ways to achieve this though ex project tool. As for the second part of your question. There is also no definite answer and it depends on what you want to know. If all of your features have a neighbour within 20km except one that is 500km away then you could miss some important trends. What I would do (if using arcGIS 10) the ISA outputs messages to the geoprocessing results thing, in there it reports the number of features that did not have a neighbour. Using this you can come up with a logical choice that is defendible. David ... View more

Hi, I too had challenges with the ISA tool. If I remember right ISA works by calculating Moran I with increasing neighbourhood sizes. Meaning Moran is calculated at each of the increments you set ex 10km 20km 30km etc. This means that each band is calculated with a different number of neighbours. My first band could have 3 neighbours and my last band could have 500 neighbours, this produced very spikey results in near bands and better results as the number of neighours increased, so you need to consider this in interpreting your results. I ended up ignoring all my moran values until a couple distance bands away from the origin. Depending on the parameters you used to perform the single Moran the value should be the same at the same distance band in the ISA tool. Ie if you set the distance band in the moran tool to 100 and the ISA had the same band value the moran values should be the same. Also, I see that you quoted your distance in dd. As Moran I is supposed to be calculated in flat space (cartesian) x and Y I would suggest projecting your data to projected coordinate system. David ... View more

Hi, I think I understand what your problem is and I think it is the result of data types. When you added your new field there is an option to set type. The type you set it to dictates what type of number can be stored, decimals, text, big numbers etc. You said the error occurred on record 32768, if you look at the info I added below you will see a short integer only stores numbers as big as 32767, ie it can not hold bigger numbers. What you should try is adding that row again setting it to long (as fid does not have any decimals). Take a look at the other info below on the other data types and scale/precision. Also, there are a million other programs you can do an ols in, R, EXCEL ... Let me know how things go. Short integer uses 16 bits to store, number range from -32768 to 32767, no decimals Long integer uses 32 bits number range -2,147,483,648 to 2,147,483,647, no decimals Float 3.4E38 to 1.2E38, ie can hold big positive numbers with decimals Double -2.2E308 to 1.8E308 ie can hold big positive and negative numbers with decimal If you pick float or double these two have additional properties you can set for rounding purposes (scale and precision) Precision: The total number of digits ie 123456789 has a precision of 9 So does 123.45678 the decimal requires one storage place Scale: Is essentially the number of decimals, ie the above has a scale of 5 *** Be aware in all other applications of math precision is essentially the number of decimals (just to make things more confusing) ... View more

Alright, I have found out why my random sampling method does not work. It is because random.sample considers the order. Ie if you have a population 1-10 and select 3 elements ex numbers 456 are drawn, this selection would be considered distinct from 654 as they were selected in a different order. I will post some correct code when I have a better sampling method. David ... View more

Most calculations of moran I require a weight matrix. There are a lot of different types, but they all essentially describe the spatial/neighbourhood relationship found in your data. This is probably what the documentation is referring to. Some of the arcGIS  calculations of Moran I do not require the input of a weight matrix (probably makes one of the fly). For row standardization, you do not always need to do this as it depends on your sampling scheme. If you are doing analysis on something like accidents it does not make sense to correct for the spatial relationship of accident sites as they physically happened there (not sampled). Your fish data would be based on a sampling scheme and thus your analysis should be row standardized (ArcGIS), you could have picked a different site and your distribution is likely not uniform in space. Regardless you should not need to change your data values as moran I is testing to see if similar values of in your case fish catch are found in similar areas. I have always felt non-confident about moran in arcgis and usually calculate it in GEODA. It is free software. You will need to calculate a weight matrix first (can be done in geoda) then perform your moran, there is documentation.  http://www.s4.brown.edu/s4/training/modul2/GeoDa2.pdf If you are bent on completing your anlysis in arcGIS, provide your error and I might be able to help with that. David ... View more

Some times I think the Moran's I output is weird from Arc. When this happens I like to calculate my Moran I with GEODA. http://geodacenter.asu.edu/software It is a free software and is really good. You can easily read shapefiles and there are good tutorials for Moran's I. Basically the steps are, calculate Weight Matrix, calculate moran I. You need to calculate the weight matrix before you can calculate moran I. David ... View more

There are a lot of things you can do and it depends on your expertise with statistics. You could start with moran I (simple in arcgis, GEODA is a free software that is a better way of calculating moran) to see if there is an overall trend of autocorrelation in house prices, ie high priced houses are near one another or not, or house prices are random. What I think is better and getting closer to what you asked would be a regression type question. To do this I would calculate the distance of each house to a train station and test for a relationship. House Price ~ Distance to train. If there is a slope in the relationship you are golden. However, in doing this analysis you will need to consider the fact that the driving factor behind the price of a house is not the distance it lies from the train but other things such as age, size, condition, yard, view etc. These factors will act as confounds to your analysis, and I expect any relationship to be somewhat weak if you can not control for these factors. Again I would suggest you do regression type analysis is a stats package. David ... View more

This is an old forum, but I use SAFE FME to do all my conversions to KML and KMZ, http://www.safe.com/ of course you need to pay for this software, but it can convert multipatch file geodatabases (3Dish), raster and vector easily with lots of control. David ... View more