Excel: if A1 in ("a", "b", "c)

https://exceljet.net/formula/cell-equals-one-of-many-things

running graphical applications without desktop env

1. install linux w/ desktop environment
2. start run level 3
3. $ X &
4. $ DISPLAY=:0 google-chrome
5. "You can switch from the X server and the framebuffer by using CTRL+ALT+F1 and CTRL+ALT+F7"

https://superuser.com/questions/407043/is-it-possible-to-run-graphical-applications-such-as-firefox-without-installing

save / print pdf without margin

Why?
pdf, including ones at research site ssrn, in general have huge margin.  when you wanna print 2 pages per sheet, the text become smaller with a lot of unnecessary white space for the margin

What do you need?
pdfcrop, which is available at ubuntu, but not centos7 afaik at the time of writing

How?
pdfcrop -h
pdfcrop <input.pdf> <output.pdf>

Appendix:
What if you don't have ubuntu?
if you have centos7 running on virtualbox with windows host, here's what I did:

1. download ubuntu 18 desktop installation iso
2. Virtualbox, existing vm, storage, optical drive
1. select the downloaded iso
2. check Live CD/DVD box
3. start VM
4. choose "Try ubuntu" after it boots from disc
5. Follow https://askubuntu.com/questions/378558/unable-to-locate-package-while-trying-to-install-packages-with-apt to update package download source
6. Open a terminal in ubuntu
1. sudo apt-get install texlive-extra-utils
2. pdfcrop <input.pdf> <output.pdf>
7. ubuntu map windows host's shared drive
1. netstat -nr to see window host's ip address from ubuntu
2. ubuntu "Files" app, which has a folder icon
3. connect to Server by entering smb://<windows ip>
8. drag and drop <output.pdf> to shared folder

Where is the source file of an imported module?

from PackageABC.ParentModule import ChildModule

import inspect
print(inspect.getsourcefile(ChildModule))

#which would be in one of these paths
import sys
for p in sys.path:
    print(p)

kdb schema idea for market depth from bid ask streams

select lUnixts:last unixts, vwap:siz wavg price, desc price, siz idesc price, siz by unixts, sym from lp where side=`BID

basically, for each timetamp, sym, there's a list of prices, the corresponding list of size, liquidity provider, etc.

see http://code.kx.com/wiki/Cookbook/ProgrammingIdioms#How_do_I_extract_regular-size_vwap_series.3F for explanation

FD whitepapers:

1. http://code.kx.com/qref/wp/sample_aggregation_engine_for_market_depth.pdf
2. http://code.kx.com/pages/db/DB_Order_Book_a_kdb+_Intra-Day_Storage_and_Access_Methodology.pdf

How to select the row value associated with the max / min of a column?

http://code.kx.com/wiki/Cookbook/ProgrammingIdioms#How_can_I_extract_the_time_of_the_lowest_and_highest_prices.3F

one way to pivot table

trade table:

stock side amount
----------------------
`ibm b 100
`ibm s 200
`appl b 300

-- sql server syntax
select stock, sum(iif(side='b', amount, 0)) as b, sum(iif(side='s', amount, 0)) as s
 from trade
 group by stock;

stock b s
------------------
`ibm 100 200
`aapl 300 0