# October 2019 Updates

• Updated the mv (move) page with information on using extended bash glob extensions to provide exclusion patterns.

$mkdir new_sub_dir # Create a new sub-directory to move all files/directories in PWD into$ mv !(new_sub_dir) new_sub_dir # Move all files/directories in PWD into new_sub_dir, excluding new_sub_dir itself (avoiding the obvious recursion problem)
• The Introduction To Rotation Matrices page has been updated with tutorials/example on how to combine rotation matrices and how to calculate the rotation matrix to describe the rotation between two reference frames, as well as a section on how to convert RPY (roll-pitch-yaw, or Euler angles) to rotation matrices.

$$\mathbf{R} = \begin{bmatrix} \hat{u_x} & \hat{v_x} & \hat{w_x} \\ \hat{u_y} & \hat{v_y} & \hat{w_y} \\ \hat{u_z} & \hat{v_z} & \hat{w_z} \end{bmatrix}$$

• Added an interactive 3D rotation visualizer to the Quaternion page, which shows you how a right-hand coordinate system XYZ is rotated in 3D space by either a rotation matrix, quaternion, or angle-axis rotation. This tool is also very useful to convert between the three ways of describing a rotation (when you enter a rotation in one notation, the other two get updated automatically).

# August 2019 Updates

• New tutorial on Standard Deviations.

• Updated the Qt page with a section on how to allow file names with capital letters in Qt Creator.

# June 2019 Updates

• The page on Electronic Noise moved from Electronics->Test And Measurement to Electronics->Circuit Design.

• Renamed the Fast Fourier Transform page to the Fourier Transform page, as it now contains information about other Fourier transforms.

• Added graphs of 1D Fourier transformations:

and animated .gifs of 2D Fourier transformations:

• Updated the pytest page with info on mark (markers) and pytest naming conventions.

• Removed the updates directory that all monthly update posts were under.

• Added a tutorial on pandas, a popular data analytics library for Python.

• Updated the Python Debugging page with more info on pdb.

• Updated the Passive Filters page with more information on low-pass RC filters, including plots of the frequency response:

• I created a public mbedded.ninja project on CircuitMaker at https://workspace.circuitmaker.com/Projects/Details/GeoffreyHunter/mbedded-ninja. I am going to trial out CircuitMaker as a tool for drawing schematic diagrams for this blog. In the past I have used Altium (not free), MultisimLive and InkScape (free but is a general vector graphics editor, not a dedicated electronics CAD program).

• Added the Command-Line CSV Viewer page, which contains information on how to cleanly view CSV files from the Linux command-line.