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formattingdisplaytabularkdb+

KDB+: Formatting Values in Tables

What is the most robust way to specify rules for formatting table values? I want to apply each rule to its corresponding column in the most efficient way. I suppose using the functional form would be helpful in this case.

Here is the sample table: 

tbl:flip `GARP`longWgt`shortWgt`longWgtBeta`shortWgtBeta`longWgtRisk`shortWgtRisk`netWgt`netExposure`relativeBeta`relativeRisk`adjBeta`adjRisk!(`GARP_AUTOS_CA`GARP_BANKS_CA`GARP_CHEMICALS_CA`GARP_COMMUNICATIONS_CA`GARP_CONS_DISCR_CA;0.0091686 0.0176234 0.0076484 0.0131509 0.0460397;-0.010305 -0.0470135 0n -0.0078549 -0.0563819;1.3522162 0.6234817 1.3140238 0.7327634 1.1802914;0.1440806 0.7642193 0n 0.7216727 0.6112765;0.3254744 0.1573925 0.2541326 0.2554008 0.350877;0.3079491 0.2218098 0n 0.2594863 0.2758658;-0.0011365 -0.0293902 0.0076484 0.005296 -0.0103422;0.8897173 0.374857 0n 1.67422 0.8165681;9.3851363 0.8158414 0n 1.0153681 1.9308631;1.0569097 0.7095833 0n 0.9842553 1.2719117;8.3501184 -3.269856 0n 1.6999496 1.5766812;-1.0634328 -3.7595078 0n 1.64786 1.0386025)

I want all the columns to have 2 significant figures. The longWgt, shortWgt and netWgt columns should be in percent.

I have something like this, but I'm sure there is a better way of doing this: 

tbl:update longWgt:100f*longWgt, shortWgt:100f*shortWgt, netWgt:100f*netWgt from tbl;
tbl:update .Q.f[2] each longWgt, .Q.f[2] each shortWgt, .Q.f[2] each longWgtBeta, .Q.f[2] each shortWgtBeta, .Q.f[2] each longWgtRisk, .Q.f[2] each shortWgtRisk, .Q.f[2] each netWgt, .Q.f[2] each netExposure, .Q.f[2] each relativeBeta, .Q.f[2] each relativeRisk, .Q.f[2] each adjBeta, .Q.f[2] each adjRisk from tbl;
tbl:update {x,"%"} each longWgt, {x,"%"} each shortWgt, {x,"%"} each netWgt from tbl;
Solution

  • How about using a functional query:

    First multiply the wgtCols below by 100:

    wgtCols: `longWgt`shortWgt`netWgt;
![`tbl;();0b;wgtCols!{(*;100f;x)} each wgtCols];

    Then format all columns allCols except the `GARP with 2 decimals:

    allCols:1_cols tbl;
![`tbl;();0b;allCols!{(each;.Q.f[2];x)} each allCols];

    Finally format the wgtCols to percentage format:

    ![`tbl;();0b;wgtCols!{(each;{x,"%"};x)} each wgtCols]

    NB: To find out how to construct your functional query, you can use the parse operator on the q-query of your choice:

    parse "update longWgt:100f*longWgt, shortWgt:100f*shortWgt, netWgt:100f*netWgt from tbl"

    Output:

    !
`tbl
()
0b
`longWgt`shortWgt`netWgt!((*;100f;`longWgt);(*;100f;`shortWgt);(*;100f;`netWgt))