You can gather information about your data by
clicking the Statistics button in the Grid Data dialog to obtain a Data Statistics Report,
checking the Grid Report option in the Grid Data dialog to create a Gridding Report,
checking the Generate Report option on the General page of the New Variogram dialog to create a Variogram Grid Report,
clicking the Display Statistics button on the Statistics page in the Variogram Properties and clicking Report to create a Variogram Grid Report,
clicking the button for a map layer in the Properties window to generate a Grid Information report,
clicking the Grids  Info  Grid Info command to obtain a Grid Information report,
clicking the Options  Grid Info command in the Grid Editor to create a Grid Information report,
or checking the Report option in the Cross Validation dialog to create a Cross Validation Report.
All reports contain the name of the report and the name of the data file. For example, a Data Statistics Report for the file demogrid.dat will be named DataStatisticsReportDemogrid. The Grid Data Report will be named GridDataReportDemogrid.
If you make changes to the data selection (i.e. changing a data column or changing the data filtering method) generate a new report by repeating one of the processes listed above. All reports contain similar information and differences are noted below.
There are 5 types of gridding reports. Each report contains different information. Some of the information is similar among the reports.
Contains Time Stamp, Data Source, Filtered Data Counts, Exclusion Filtering, Duplicate Filtering, Breakline Filtering, Data Counts, Univariate Statistics, InterVariable Covariance, InterVariable Correlation, InterVariable Rank Correlation, Principal Component Analysis, Planar Regression: Z = AX+BY+C, and Nearest Neighbor Statistics. See below for a list of the information contained in each section. The data statistics always refer to the pretransformed Z values, even when the Log, save as log or Log, save as linear option is selected when gridding.
Contains Time Stamp, Data Source, Filtered Data Counts, Exclusion Filtering, Duplicate Filtering, Breakline Filtering, Z Data Transform, Data Counts, Univariate Statistics, InterVariable Covariance, InterVariable Correlation, InterVariable Rank Correlation, Principal Component Analysis, Planar Regression: Z = AX+BY+C, Nearest Neighbor Statistics, Gridding Rules, and Output Grid. See below for a list of the information contained in each section.
Contains Time Stamp, Grid Information, Grid Geometry, and Univariate Grid Statistics. See below for a list of the information contained in each section.
ContainsTime Stamp, Data Source, Gridding Rules, Data Counts at Validation Points, Univariate Statistics, Univariate CrossValidation Statistics, Residual Regression at Validation Points: R = AX+BY+C, InterVariable Correlation at Validation Points, and Rank Correlation at Validation Points. See below for a list of the information contained in each section.
Contains Data Source, Variogram Grid, Data Counts, Univariate Statistics, InterVariable Correlation, InterVariable Covariance, Planar Regression: Z = AX+BY+C, Nearest Neighbor Statistics, Exclusion Filtering, and Duplicate Filtering. See below for a list of the information contained in each section.
Each section of the report contains information about the grid, data, or variogram.
Time of report 
Date and time the report was created in Mon Oct 14 10:43:13 2013 format 
Elapsed time to create grid 
Seconds required when gridding. Only included in the Gridding Report. 
Source Data File Name 
path and file name of the data used in gridding 
X Column 
X data column 
Y Column 
Y data column 
Z Column 
Z data column 
Detrending 
variogram data detrending method selected on the General page in the New Variogram dialog. Only included in the Variogram Grid Report. 
Active Data 
number of data after applying filters 
Original Data 
number of original data points (excludes breakline data) 
Excluded Data 
number of data excluded by the Data Exclusion Filter  the excluded data are listed in the Exclusion Filtering section 
Deleted Duplicates 
number of duplicates deleted by the Duplicate Data filter  the deleted duplicates are listed in the Duplicate Filtering section 
Retained Duplicates 
number of duplicates retained by the Duplicate Data filter (this statistic is not computed if the duplicate rule is ALL)  the retained duplicates are listed in the Duplicate Filtering section including any artificial data 
Artificial Data 
number of artificial data created by the Sum, Average, and Midrange Duplicate Data filters 
Superseded Data 
Superseded data are number of data eliminated by breaklines in the Data Statistics Report and the Gridding Report. Breakline data always supersede point data. If point data are on, or in the immediate vicinity of, breakline data the point data are eliminated. 
The Data Counts at Validation Points section is only included in the Cross Validation Report.
Active Results 
locations at which the cross validation interpolation was successfully carried out 
Blanked Results 
The blanked results are the locations at which cross validation interpolation was attempted, but was not successful. For example, the natural neighbor gridding algorithm can only interpolate at locations within the convex hull of the active data. As such, an observation that lies on the convex hull of the original, complete, data set will lie outside of the convex hull of the active data when that observation is the cross validation point. Cross validation is not possible using the natural neighbor algorithm at such a point, so it is blanked. 
Attempted Results 
reports the number of locations at which cross validation interpolation was attempted 
Requested Results 
contains the original number of random data 
Includes the transformation method (if any) applied to the Z values. Lists the data that was unable to be transformed in a table.
The rest of the report information is calculated using the active data, including any artificial data generated by duplicate filtering. Excluded, deleted, or superseded data are not included in the following calculations.
Exclusion Filter String 
shows the Data Exclusion Filter string 
Excluded Data 
number of data excluded by the Data Exclusion Filter  
Excluded Data Table 
the excluded data are listed in a table. The ID is equal to the line number in the original data file. This list is 100 data rows long by default. 
Duplicate Points to Keep 
To Keep filter used 
X Duplicate Tolerance 
maximum X spacing of points to be considered a duplicate 
Y Duplicate Tolerance 
maximum Y spacing of points to be considered a duplicate 
Deleted Duplicates 
number of duplicates deleted by the Duplicate Data filter  the deleted duplicates are listed in the Duplicate Filtering section 
Retained Duplicates 
number of duplicates retained by the Duplicate Data filter (this statistic is not computed if the duplicate rule is ALL)  the retained duplicates are listed in the Duplicate Filtering section including any artificial data 
Artificial Data 
number of artificial data created by the Sum, Average, and Midrange Duplicate Data filters 
Duplicate Data Table 
the duplicate data table lists all of the duplicate points with X, Y, Z, ID, and Status. The ID is equal to the line number in the original data file. When the status is artificial, no ID is given since this data does not come from the original data file. The Status (Retained, Deleted, or Artificial) reports how the duplicate was handled. This list is 100 data rows long by default. 
When breaklines are used, data that is within the X Tolerance and Y Tolerance, as set in the Filter dialog, of the breakline are deleted due to breakline data superseding original data.
Anisotropy Angle 
the anisotropy angle reported for the default variogram 
Anisotropy Ratio 
the anisotropy ratio reported for the default variogram 
X Tolerance 
maximum X spacing of points to be considered a duplicate 
Y Tolerance 
maximum Y spacing of points to be considered a duplicate 
Superseded Data 
Superseded data are number of data eliminated by breaklines in the Data Statistics Report and the Gridding Report. Breakline data always supersede point data. If point data are on, or in the immediate vicinity of, breakline data the point data are eliminated. 
Breakline Data Table 
the breakline data table lists all of the superseded data points with X, Y, Z, ID, and Status. The ID is equal to the line number in the original data file. The Status (Retained, Deleted, or Artificial) reports how the duplicate was handled. This list is 100 data rows long by default. 
The InterVariable Correlation table shows the correlation between the X, Y, and Z variables. The Cross Validation Report also contains Estimated Z and Residual Z columns and rows. The correlations are computed with
The correlation is positive when both variables increase or decrease together. The correlation is negative when one variable increases while the other variable decreases. A correlation of zero shows that there is no linear relationship between the variables.
The InterVariance Covariance table shows the covariance between the X, Y, and Z variables. The covariances are computed with
The covariance is positive if, on average, the variables are both above the mean. The covariance is negative if one variable is above the mean and the other variable is below the mean.
The InterVariance Rank Correlation table shows the rank correlation between the X, Y, and Z variables. The data is ordered and then assigned a rank value from 1 to the count of values. Rank values range from 1 to +1. The correlation is positive when both variables increase or decrease together. The correlation is negative when one variable increases while the other variable decreases. A correlation of zero shows that there is no linear relationship between the variables.
This group of statistics shows information for X, Y, and Z data. These statistics do not include breakline data.
Count 
total number of points 
1%%tile 
1 percent of the values are smaller than this number and 99 percent of the values are larger 
5%%tile 
5 percent of the values are smaller than this number and 95 percent of the values are larger 
10%%tile 
10 percent of the values are smaller than this number and 90 percent of the values are larger 
25%tile 
lower quartile; 25 percent of the values are smaller than this number and 75 percent of the values are larger 
50%%tile 
middle data value, 50 percent of the data values are larger than this number and 50 percent of the data are smaller than this number 
75%tile 
upper quartile; 75 percent of the values are smaller than this number and 25 percent of the values are larger than this number 
90%%tile 
90 percent of the values are smaller than this number and 10 percent of the values are larger 
95%%tile 
95 percent of the values are smaller than this number and 5 percent of the values are larger 
99%%tile 
99 percent of the values are smaller than this number and 1 percent of the values are larger 
Minimum 
minimum value 
Maximum 
maximum value 
Mean 
arithmetic average of the data 
Median 
middle data value, 50 percent of the data values are larger than this number and 50 percent of the data are smaller than this number 
Geometric Mean 
geometric mean of the data 
Harmonic Mean 
harmonic mean of the data 
Root Mean Square 
square root of the mean square 
Trim Mean (10%) 
Trim Mean is the mean without the upper five percent and lower five percent of the data, therefore, extreme value influence is removed. If there are fewer than 20 data points, the minimum and maximum data points are removed instead of the upper and lower five percent. 
Interquartile Mean 
interquartile mean, or midmean, is a truncated mean using only the data in the second and third quantiles (all data beween the 25%%tile and 75%%tile) 
Midrange 
the value halfway between the minimum and maximum values Midrange = (Minimum + Maximum ) / 2 
Winsorized Mean 
Winsorized mean is a truncated mean. This method replaces the extreme highs and lows values with a more central value. This mean is less sensitive to outliers. 
TriMean 
the trimean, or Tukey's trimean, is a measure of probability distribution location. This is equivalent to the the sum of (quartile 1, 2 times the quartile 2, and quartile 3) divided by four. 
Variance 

Standard Deviation 
square root of the variance 
Interquartile Range 
separation distance between the 25%tile and 75%tile this shows the spread of the middle 50 percent of the data, similar to standard deviation, though this statistic is unaffected by the tails of the distribution 
Range 
separation between the minimum and maximum value Range = Maximum  Minimum 
Mean Difference 
the mean or average of the absolute difference of two random variables X and Y. 
Median Abs. Deviation 
Median Absolute Deviation is the median value of the sorted absolute deviations. It is calculated by 1. computing the data's median value 2. subtracting the median value from each data value 3. taking the absolute value of the difference 4. sorting the values 5. calculating the median of the values 
Average Abs Deviation 
Average Absolute Deviation is the average value of the sorted absolute deviations. It is calculated by 1. computing the data's average mean value 2. subtracting the mean value from each data value 3. taking the absolute value of the difference 4. calculating the average value 
Quartile Dispersion 
Measures dispersion of the data using: (Quartile 3  Quartile 1)/(Quartile 3 + Quartile 1) 
Relative Mean Difference 
The mean difference of the entire data set divided by the sample mean of the data set 
Standard Error 
The standard error of the mean is the standard deviation of those sample means over all possible samples drawn from the population. This is calculated by dividing the standard deviation by the square root of the number of samples. 
Coef. of Variation 
The Coefficient of Variation is calculated by dividing the standard deviation by the mean. If a "1" is reported, the coefficient of variation could not be computed. The coefficient of variation is computed only for the Z values. 
Skewness 
The Coefficient of Skewness is calculated by If a "1" is reported, the coefficient of skewness could not be computed. The coefficient of skewness is computed only for the Z values. 
Kurtosis 
The Coefficient of Kurtosis is calculated by 
Sum 
the sum of all X, Y, or Z values 
Sum Absolute 
the absolute value of the sum of all X, Y, or Z values 
Sum Squares 
the sum of all squared X, Y, or Z values 
Mean Square 
Planar regression is an ordinary leastsquares fit where Z=AX+BY+C.
The Parameter Values are the A, B, and C values.
The Standard Error is the estimated standard deviation of the parameters.
The InterParameter Correlations are the correlation between A, B, and C coefficients.
The ANOVA Table shows regression statistics on the planar fit where df are the degrees of freedom and F is the ratio of the mean squares.
The Coefficient of Multiple Determination (R2) is calculated with
For the Cross Validation Report, the planar regression is the residual regression at the validation points.
The nearest neighbor statistics represent aspects of the data values and of the data locations. The nearest neighbor to a data point uses a simple separation distance without taking anisotropy into account. If two or more points tie as the nearest neighbor, the tied data points are sorted on X, then Y, then Z, and then ID. The smallest value is selected as the nearest neighbor.
The Separation column shows the separation distances between the observation and its nearest neighbor. The Delta Z column shows the absolute values of the differences between the observation Z value and the nearest neighbor Z value.
The statistics are the same as the Univariate Statistics (see above).
The Nearest Neighbor Statistics also includes the Complete Spatial Randomness section. The Complete Spatial Randomness statistics measure how random locations are in space. Surfer does not correct for edge effects so the statistics may be biased.
Lamda 
is the average spatial density

Clark and Evans 
where = average spatial density Si = separation distance between the observation and the nearest neighbor
The distribution of this statistic is normal, with a mean equal to one and a variance of
See Clark and Evans (1954) and Cressie (1991) for more information.

Skellam 
where = average spatial density Si = separation distance between the observation and the nearest neighbor
The distribution is ChiSquared with 2N degrees of freedom. See Skellam (1952) and Cressie (1991) for more information. 
Principal component analysis (PCA) is a mathematical procedure that uses orthogonal transformation to convert a set of observations of possibly correlated variables into a set of values of linearly uncorrelated variables called principal components. The number of principal components is less than or equal to the number of original variables. The principal components are calculated for the X, Y, and Z values. A value is also reported for each principal component.
Max Lag Distance 
Max Lag Distance set on the General page in the New Variogram dialog 
Angular Divisions 
number of Angular Divisions set on the General page in the New Variogram dialog 
Radial Divisions 
number of Radial Divisions set on the General page in the New Variogram dialog 
Output Grid
Grid File Name 
name of the output grid file 
Grid Size 
number of rows and columns in the grid 
Total Nodes 
number of columns times the number of rows 
Filled Nodes 
number of grid nodes containing interpolated values 
Blanked Nodes 
number of grid nodes containing blanked values 
X Minimum 
minimum X grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
X Maximum 
maximum X grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
X Spacing 
X spacing set in the Grid Data dialog 
Y Minimum 
Minimum Y grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
Y Maximum 
Maximum Y grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
Y Spacing 
Y spacing set in the Grid Data dialog 
Grid Information
Grid File Name 
name of the output grid file 
Grid Size 
number of rows and columns in the grid 
Total Nodes 
number of columns times the number of rows 
Filled Nodes 
number of grid nodes containing interpolated values 
Blanked Nodes 
number of grid nodes containing blanked values 
Blank Value 
reports the Z value associated with blanked nodes 
Grid Geometry
X Minimum 
minimum X grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
X Maximum 
maximum X grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
X Spacing 
X spacing set in the Grid Data dialog 
Y Minimum 
Minimum Y grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
Y Maximum 
Maximum Y grid line value specified in the Output Grid Geometry group in the Grid Data dialog 
Y Spacing 
Y spacing set in the Grid Data dialog 
This section displays the gridding method used, as well as the option settings for each gridding method.
The Univariate Grid Statistics are the same as those reported in the Univariate Statistics and Nearest Neighbor Statistics sections.
The Univariate Cross Validation Statistics section are the same as those reported in the Univariate Statistics. It also contains an additional column of data, called Data Used. This column shows the number of data points used in the calculation.
See Also