R data.table apply function to sum of two columns -


i have data.table, , i'd apply function on columns. done so:

dt[, lapply(.sd, func), .sdcols = c("col1", "col2")]

and apply function func on 2 columns. if, however, i'd apply on sum of 2 columns? like

dt[, lapply(.sd, func), .sdcols = "col1 + col2"]

obviously doesn't work.

you generalise applying func result of function (in case, sum) takes in columns arguments. know can create column containing results of first function, there way around that?

to add columns, try

dt[, func(reduce(`+`,.sd)), .sdcols = c("col1","col2")]

this works more 2 columns well, adding them before applying func.


Comments

Post a Comment

Popular posts from this blog

python - Mongodb How to add addtional information when aggregating? -

i beginner , wrote line pipeline works, wanna add other information output, screen name , or number of tweets.i tried add under $group gave me syntax error everytime here pipeline: def make_pipeline(): # complete aggregation pipeline pipeline = [ { '$match': { "user.statuses_count": {"$gt":99 }, "user.time_zone": "brasilia" } }, { "$group": { "_id": "$user.id", "followers": { "$max": "$user.followers_count" } } }, { "$sort": { "followers": -1 } }, { "$limit" : 1 } ]; i using on example : { "_id" : objectid("5304e2e3cc9e684aa98bef97"), "text" : "first week of school on :p", "in_reply_to_status_id" : null, "retweet_count" : null, ...
Read more

java - Spring Data JPA: Why findOne(id) executing delete query internally? -

i have 1 application using @manytomany annotation link 2 different entities 1 parent entity. not sure if have implemented properly. when execute .findone() on parent entity's repository find it, @ first fetch data along executing delete queries internally delete record mapping table (a table jpa creates after adding @manytomany annotation.). following generated sql queries , code snippet: java class @entity @table(name = "inventory") public class inventory { @id long id; // many other properties @manytomany(fetch=fetchtype.lazy) private list<stream> streams; @manytomany(fetch=fetchtype.lazy) private list<subject> subjects; } there no other annotation i've put in stream , subject entity class link inventory class. when run app, create following tables: inventory stream subject inventory_stream inventory_subject (inventory_stream , inventory_subject, 2 tables created automatically, don't k...
Read more

ruby - Net::HTTP extremely slow responses for HTTPS requests -

for reason, on development machine i'm getting very, slow responses https requests performed via net::http. i've tried restclient , httparty , both have same issue. seems have sprung nowhere. i've made these requests hundreds of times without issue, today unbearably slow. pry(main)> puts time.now; httparty.get('https://api.easypost.com/v2/addresses'); puts time.now; 2015-04-29 08:07:08 -0500 2015-04-29 08:09:39 -0500 as can see, response took 2.5 minutes. , it's not easypost api url. i've tried numerous ssl requests servers know can connect ( https://google.com , https://weather.com , etc.) , result in same behavior. also, noticed same thing happens requests redirected http https. now, check out non-ssl request: pry(main)> puts time.now; httparty.get('http://lookitsatravis.com'); puts time.now; 2015-04-29 08:12:22 -0500 2015-04-29 08:12:22 -0500 instantaneous. gives? guess configuration problem somewhere between ruby , openssl. i...
Read more