POST

Hi John, Thank you for your reply. I tried checking geometry and creating a new project, but it did not help. As to tolerance settings, I did not take that into account. I guess I would have to create topological relationships first, if I am not wrong?
... View more
11252013
03:10 AM

0

0

2

POST

Hello, I am using the Intersect tool to find which points in one shapefile are located within different polygons in another shapefile. The problem that I have come accross is that a half of the points in the newly created shapefile are duplicated. They are not located on the border of the polygons but within them. I can use Delete Identical to get rid of these duplicates but I want to know why this is happening. If I intersect the same polygon layer and another point layer (with different locations), the shapefile with duplicates is not produced (so, everything seems to be ok). All of the point layers I am dealing with are originating from the excel file containing GPS coordinates which I have exported as a point shapefile. Thank you.
... View more
11212013
09:20 PM

0

3

801

POST

Hello, I am not sure if I understand properly what is the meaning of the existence of large scale spatial variation in the mean value when first order effect is present. The spatial pattern that is the result of the process is only concerned with locational information, not attribute information, so what do nonconstant variance and mean in space actually pertain to? It will be helpful if someone can also provide simple illustrative example of this locational dependence of mean and variation in space. Thank you.
... View more
03122013
01:31 PM

0

1

4481

POST

Hello everyone, I plan to include coordinates as covariates in the regression equation in order to adjust for the spatial trend that exists in the data. After that, I want to test residuals on spatial autocorrelation in random variation. I have several questions: 1. Should I perform linear regression in which only independent variables are x and y coordinates and then tests residuals on spatial autocorrelation, or should I rather include not only coordinates as covariates but also other variables and then test residuals. 2. If I expect to have quadratic trend, and then include not only x,y, but also , xy, x squared and y squared, but then some of them (xy and y squared) have the pvalue higher than the threshold should I exclude those variables with higher pvalue as being nonsignificant? How should I then interpret the trend, it is certainly not quadratic anymore? 3. I guess I should treat x and y coordinates as any other covariates, and test them on having linear relationship with dependent variable by constructing partial residual plots ... but then once I transform them (if they show they need transformation), that will not be that kind of trend any more (especially if I include xy, x squared and y squared for quadratic trend). It may show that x squared, for example, needs transformation, while x does not or so? How should I react in these situations? Thank you.
... View more
07052012
02:33 AM

0

1

1618

POST

Hello Jeffrey, Thank you a lot for your reply. But is it necessary first to remove or account for trend in the data and then deal with spatial autocorrelation, since I plan to include spatial effects in covariates by using spatial lag regression? If I plan to include in regression equation coordinates as covariates (in order to adjust for existing trend), but I expect, for example, to have quadratic trend, then I will have to include also x sqaured and y squared as variables, right? What if I get pvalues for x squared and y high (so that I have to exclude them) and thus only able to keep y squared and x. What kind of trend is there in my data in that case? Or I do not have to focus on that too much, but just include those forms of coordinate variables (along with outer independent variables) that appear significant in my regression?
... View more
07042012
02:39 AM

0

0

0

POST

Hello everyone, I have a question regarding performing spatial regression on data which residuals are spatially correlated. If the residuals are spatially autocorrelated due to the presence of trend, how should I account for the existence of spatial autocorrelation? And what about if there is no trend, but rather spatial autocorrelation in random variation (in residuals left after detrending)? And what about if there are both trend and spatially autocorrelated random variation in my data? Can I in both cases apply this formula to account for spatial autocorrelation no matter if it is the result of trend or random variation correlation: y*=yρ???(w_ij*y_j) x*=xρ???(w_ij*x_j) Thanks!
... View more
07022012
09:34 AM

0

2

138

POST

Hello everyone, I am a bit confused about the resulting semivariogram I've got after detrending. The value of the sill is zero and it seems that the theoretical variogram is non existent. What does this result indicate? I have attached the two semivariogram (detrended and with trend). Thank you.
... View more
06292012
12:07 PM

0

2

2629

Online Status 
Offline

Date Last Visited 
2 weeks ago
