{{ message }}

Instantly share code, notes, and snippets.

# denis-bz

Last active Jun 25, 2022
Poisson2 - 4 I: nice test matrices for linear solvers and eigensolvers 25 Jun 2022
View 0-Poisson-matrices.md

## 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\$

Created Jun 21, 2022
One-line queries of the SuiteSparse matrix collection 21 Jun 2022
View ssquery.py
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
 #!/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
Last active Mar 26, 2022
HUSL rgb_to_lch is not CIELCh
View 0-HUSL-lch-is-not-CIELCh.md

### 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: \

Last active Feb 28, 2022
Are windspeeds and capacity factors from https://globalwindatlas.info linearly related ? 24 Dec 2021
View 0-globalwindatlas-linear.md

#### 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.

Created Nov 30, 2021
How does wind power vary with wind speed, Weibull model ? 30 Nov 2021
View 0-Windpower-Weibullmodel.md

### 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.)

Last active Feb 28, 2022
Windfarms in Germany, from de.wikipedia 14 Nov 2021
View 0-Windfarms-in-Germany.md

#### 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

Created Nov 7, 2021
Basic image warping or map reproject in python 7 Nov 2021
View 0-warp.md

### 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

Last active Sep 13, 2021
rioxarray reproject UTM -> 4326 widens NaNs at the sides 13 Sep 2021
View 0-warp_raster_test.md

#### 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:

Last active Jul 12, 2021
Electricity in Germany from coal, wind etc.
View 0-German-energy.md

#### 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

Created Jun 10, 2021
Read German Corona data rki.de/.../Fallzahlen_Kum_Tab.xlsx in python pandas
View rki_excel.py
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
 #!/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