denis-bz

Poisson2 - 4 I: nice test matrices for linear solvers and eigensolvers

Purpose: a simple generator of test matrices for linear solvers and eigensolvers

Keywords: sparse-matrix, linear-solver, eigensolver, arpack, nullspace, python

poisson2( n ) below generates sparse $n^2 \ x \ n^2$ matrices $A$ with $A$ symmetric (aka Hermitian) and positive-definite; solving $A \ x = b$ is then relatively easy. $A_4 = A - 4 I$ is more interesting: there are $n$ vectors $z_i$

denis-bz

#!/usr/bin/env python3
""" Usage:
python3 ssquery.py  '(posdef == 1)  &  (1000 <= rows <= 20000)'  posdef.csv
reads http://sparse.tamu.edu/files/ssstats.csv 
queries it
writes "posdef.csv" like

# SuiteSparse  posdef  &  (1000 <= rows <= 20000) 
id,group,name,rows,cols,nnz,real,bool,is2d3d,posdef,symm,nsymm,kind
29156,Boeing,msc01050,1050,1050,26198,1,0,1,1,1.0,1.0,structural

denis-bz

HUSL rgb_to_lch is for CIELuv, not CIELab

Keywords: color-space HUSL HSLuv CIELCh CIELuv CIELab max-chroma everyone-knows

_{Whenever something can be done in two ways, someone will be confused.}

There are two quite different color spaces: \

denis-bz

Are windspeeds and capacity factors from https://globalwindatlas.info linearly related ?

Keywords: wind power, Germany, python, globalwindatlas

I'd appreciate hearing from anyone who knows how globalwindatlas calculates its data.

denis-bz

How does wind power vary with wind speed, Weibull model ?

Keywords: wind power, wind energy, model, Weibull, python

Purpose: a simple model of wind power, power curve × Weibull wind curves.

Look at the map of windspeeds in Germany under globalwindatlas.info: set the height to 150m and windspeeds to say 6 to 9 m/s in the sidebars. (I'd show it here, but it's copyrighted.)

denis-bz

Windfarms in Germany from de.wikipedia

Keywords: wind power, Germany, python, globalwindatlas

Purpose: collect data on wind farms in Germany in a single .csv file, from https://de.wikipedia.org/wiki/Liste_von_Windkraftanlagen_in_Bayern etc.

The file windfarms-in-Germany.csv looks like this:

MW MW/Rad Nrad Year N E Land Lkr Typ Ort

denis-bz

Warping maps or images

Keywords: image raster resize rescale reproject Manhattan-grid regular-grid

We have a picture (image, raster) A, an array of colored pixels, and want to warp it to a new picture O of a different size or shape. Examples: Map projection, flat maps <-> globe; Image scaling.
There are hundreds of cases of these, and zillions of programs

denis-bz

rioxarray reproject UTM -> 4326 widens NaNs at the sides

Keywords: rioxarray, rasterio, reproject, geotiff, testcase

This plot shows that rioxarray reproject UTM -> 4326, middle -> right, widens NaNs at the sides:

denis-bz

Electricity in Germany from coal, wind etc.

Keywords: electricity, Germany, renewable, wind, python, pandas

Purpose: summarize data on electricity sources in Germany from the electricity market site smard.de:

total 502489 GWh  365 days, 2020-07-01 .. 2021-06-30:
                 GWh    %   GW

Braunkohle 96253.2 19.2 11.0

denis-bz

#!/usr/bin/env python3
""" https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Daten/Fallzahlen_Kum_Tab.html .xlsx
    -> python pandas read_excel
"""
# sheets, from openpyxl --
#  0    Erlaeuterungen  20 rows  1 cols
#  1    Fälle-Todesfälle-gesamt  509 rows  16384 cols  ?!
#  2    BL_7-Tage-Fallzahlen (fixiert)  39 rows  396 cols
#  3    BL_7-Tage-Inzidenz (fixiert)  21 rows  396 cols
#  4    LK_7-Tage-Fallzahlen (fixiert)  419 rows  207 cols