DolphinDB is a high performance time series database. It is written in C++ and optimized for fast injection, storage, retrieval and analysis of time series data in fields such as quantitative finance, Internet of Things, real-time analytics, etc. DolphinDB runs extremely fast. It is also easy to use as the syntax of the programming language of DolphinDB is similar to SQL and Python.
Questions tagged [dolphindb]
764 questions
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In DolphinDB, how do i Import data for special time types?
I have data as follows:
Identifier, Domain, DateTime, GMT Offset, Type, Bid, Ask, ExchTime, BidYld, AskYld, Date
CN180210=,MarketPrice, 2019-01-01T00:07:30.456396320Z,0,Quote,103.124,103.732,,3.643,3.568,2019/1/2
...
How should I handle…
dovish618
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In DolphinDB, I have a table A storing the futures contract info, how to efficiently retrieve continuous tick data using A?
There is an application scenario: if I have a table A, which is the contract name corresponding to different dates. Now I want to get continuous tick data based on this table (the specific contract for different dates is determined by table A). If I…
dovish618
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Does DolphinDB support -inf and inf when dividing by 0 like numpy?
I know in Numpy, if it is divided by 0, it could become -inf or inf. In DolphinDB, if dividing by 0, it will turn into NULL, it is hard for me to tell if the value is just NULL or caused by 0 division.
rc618
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Parameter for upper and lower bound in linear programming solvers
Many scientific computing platforms provide a linear programming solver. For example, there is a linprog function in MATLAB, Scipy, and DolphinDB. And linprog in all those three platforms provides a parameter for inequality constraints, namely A,…
Clyx
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How to read text file in dolphindb?
The dolphindb manual says it can read file like
fin = file("C:/DolphinDB/test.txt")
x=fin.readLine()
But readLine() will return a string of this row.
I have a text file like:
1 2 3 4 5 6 7 8 9
How can I get these nine digits one by one ?
Robin Zhang
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Why get back this error message when I subscribe in DolphinDB java api
I have a table in dolphindb:
t = streamTable(30000:0,`id`time`sym`qty`price[INT,TIME,SYMBOL,INT,DOUBLE])
share t as Trades
And I want to subscribe this table in java client.
PollingClient client = new PollingClient(8892);
TopicPoller poller1 =…
xxq1024
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In the function of createTimeSeriesAggregator of DolphinDB, what's the relationship between window size and steps?
In the function of createTimeSeriesAggregator of DolphinDB, what's the relationship between window size and parameter step? When is the first execution get triggered with or without using parameter "useWindowStartTime"?
rc618
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Can Orca be used to operate on a DolphinDB stream table?
I was trying to append data to a stream table through the Orca API (pandas project of DolphinDB).
It seems that it doesn't work. Will Orca support operations on streams tables?
e.g.
orca.load_table(THE_STREAM_TABLE)
is not working.
rc618
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How to improve performance in calculating greeks in DolphinDB?
I am using DolphinDB to calculate Greeks, I wrote it in vectorized way, and the performance is quite good. But I can't implement implied volatility in vectorized way which makes the performance very poor. How can I improve the performance of the…
Ju Piece
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How do I upload DATETIME data with DolphinDB Python API
I was trying to upload some DATETIME data with DolphinDB Python API. I tried the following code.
from datetime import datetime
import dolphindb as ddb
sess = ddb.session('localhost', 8848)
sess.upload({'t': datetime(2020, 2, 2)})
But I got the…
Clyx
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Does the DolphinDB language support not in syntax?
Suppose I have the following table,
t=table(1..5 as id,6..10 as v)
I want to select the records from the table where id != 2 and id !=4 ,but I execute the following code ,
select * from t where id not in (2,4)
The error message is as…
smile qian
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1 answer
How to append to a DolphinDB database in-memory table with Python API?
I ran the following code in python to append to a DolphinDB database in-memory table:
import dolphindb as ddb
import pandas as pd
import numpy as np
s = ddb.session()
s.connect("localhost", 8848, "admin", "123456")
script = """t =…
JHPowderDays
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2 answers
How to remove duplication row from dolphindb table?
How to select non duplicate row data from the table of DolphinDB? I found the function distinct in the manual. I tried the code below, but doesnt work.
select distinct(col1,col2) from table
=====================================
The function…
HIPO.L
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How to set data retention time in DolphinDB?
I would like to store device data in DolphinDB and keep data for 3 month. It is trouble to drop data manually by function dropPartition every 3 months. Can DolphinDB clear expired data automatically? Dose DolphinDB have retention policy like…
Winter.Z
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can't upload DataFrame with NaN with DolphinDB python api
While I was trying to upload some data to dolphindb server using python api, I found that dolphindb server will refuse to accept it and throw an exception if my dataframe contains null values. The following code could reproduce this.
import…
siupan
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