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# Category Archives: Coordinate Geometry

## More circle fitting options with Scipy

A comment on the first post on this topic found that the method used did not work well for short arcs of large radius circles. An example of the problem can be seen in the screen shots below: The function … Continue reading

Posted in Coordinate Geometry, Curve fitting, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA, xlwings
Tagged curve fitting, Excel, least squares, Numpy, ODR, Python, SciPy, VBA
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## More Python rotation functions

The code described in the previous post includes a Python function that rotates 3D coordinates by an angle defined with two vectors, using Rodrigue’s Rotation. I have now added this function to the IP2_py spreadsheet, where it is used in the … Continue reading

Posted in Coordinate Geometry, Drawing, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA, xlwings
Tagged Excel, fit 3D circle, Numpy, Python, RPView, UDF, VBA, xlwings, xl_RPView
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## Fitting 3D circles to scattered points

Following a comment at update-to-glob_to_loc3-and-loc_to_glob3-functions, I have modified the Python code at the linked site, so it can be run from Excel, via xlwings. The spreadsheet described below, and the associated Python code, can be download from: 3DCirc.zip The original … Continue reading

Posted in Coordinate Geometry, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA, xlwings
Tagged 3DCirc, Excel, fit 3D circle, Numpy, Python, UDF, VBA, xlwings
5 Comments

## Update to Glob_to_loc3 and Loc_to_glob3 functions

Following a comment here I have updated the Glob_to_loc3 and Loc_to_glob3 functions to deal with some problems when the local longitudinal axis is parallel to the global Y or Z axes. The IP2 spreadsheet, including the revised functions, can be downloaded from: … Continue reading

Posted in Coordinate Geometry, Excel, Finite Element Analysis, Frame Analysis, Newton, UDFs, VBA
Tagged Excel, global axes, Glob_to_Loc3, local axes, Loc_to_Glob3, UDF, VBA
6 Comments

## Nearest Lookup Function

The Excel Lookup functions (including VLookup, HLookup and Match) all allow for an “exact” or “closest” match on numerical data, but the closest option has a number of problems: The data must be sorted For VLookup and HLookup the data … Continue reading

Posted in Coordinate Geometry, Excel, Maths, UDFs, VBA
Tagged Dist, Excel, HLookup, Match/Index, Nearest, Problems with Lookups, UDF, VBA, VLookup
2 Comments

## IP2 and IP2_py

The IP2 spreadsheet provides functions to calculate: Intersection points of 2D lines or polylines Intersection points of 2 circles, or a line and a circle Intersection circle of two spheres and intersection points of 3 spheres 3D centre point of … Continue reading

## Dividing shapes into layers

For reasons that will become apparent in a later post, I need to rotate irregular polygons, defined by the coordinates of each corner, by a specified angle, and then split the resulting shape into horizontal trapezoidal layers. I have written … Continue reading

Posted in Coordinate Geometry, Excel, Maths, UDFs, VBA
Tagged divide shape into layers, Excel, rotate coordinates, section properties, UDF, VBA
8 Comments