Using API to download data from the Statistics Sweden database (works) and from the NIER database (works not, error message)

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Lars Svensson
Lars Svensson 2023-1-31
回答： Lars Svensson 2023-2-14
This script works for downolading from the Statistics Sweden database,
http://www.statistikdatabasen.scb.se/pxweb/en/ssd/START__NR__NR0103__NR0103C/SektorENS2010KvKeyIn/
%% SCB
url = 'https://api.scb.se/OV0104/v1/doris/en/ssd/START/NR/NR0103/NR0103C/SektorENS2010KvKeyIn';
opts = weboptions('ContentType','auto');
% Whole table
jsonQuery1 = '{"query":[],"response":{"format": "csv"}}';
response1 = webwrite(url, jsonQuery1, opts); % Output is Table in Matlab
Data1 = response1{:,3:end};
Here, response1 is an 18x173 table, and Data1 is an 18x173 matrix. This is perfect for my needs.
However, suppose I try to apply this to the database of the National Institute of Economic Research, for example this table,
http://prognos.konj.se/PxWeb/pxweb/en/SenastePrognosen/SenastePrognosen__f12_hushallensdisponiblainkomster/F1201.px/table/tableViewLayout1/ ,
with the url for the API ,
http://prognos.konj.se/PxWeb/api/v1/en/SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px
Thus, suppose I apply this:
url = 'http://prognos.konj.se/PxWeb/api/v1/en/SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px';
opts = weboptions('ContentType','auto');
% {
% "query": [],
% "response": {
% "format": "px"
% }
% }
jsonQuery = '{"query":[],"response":{"format":"csv"}}';
response = webwrite(url,jsonQuery,opts);
Then I get the following error message:
Error using readContentFromFile
The content reader issued the error message: "'.px' is not a recognized file extension. Unable to detect file type. To read the file as a specific file type, regardless of file extension, use the 'FileType' name-value pair.", while reading the content downloaded from URL
'http://prognos.konj.se/PxWeb/api/v1/en/SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px'. Use the function WEBSAVE to save the content to a file.
Error in readContentFromWebService (line 66)
readContentFromFile(filename, charSet, urlContentType, options, url);
Error in webwrite (line 139)
[varargout{1:nargout}] = readContentFromWebService(connection, options);
Can you help me solve this and make "response" be a Matlab table?

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采纳的回答

Lars Svensson
Lars Svensson 2023-2-14
Dear Amit,
Thank you very much for this solution and the links.
An alternative solution I just found is the following:
% Download from NIER, set "format" to "csv"
url = ['http://prognos.konj.se/PxWeb/api/v1/en/' ...
'SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px'];
opts = weboptions('ContentType','text');
query = '{"query":[],"response":{"format":"csv"}}';
Response = webwrite(url,query,opts);
% Save Response as a text file: response.csv
% Following https://www.mathworks.com/matlabcentral/answers/506670-how-to-create-a-txt-file-from-char-vector-using-matlab
filename = 'Response.csv';
fid = fopen(filename,'w'); % Open file for writing (overwrite if necessary)
fprintf(fid,Response); % Write the char array
fclose(fid); % Close the file
% Finally use readtable to create the table
T = readtable(filename,'ReadVariableNames',true,'VariableNamingRule','preserve');
The resulting table T equals the full table on the NIER website.
A question: Is it possible to import Response directly as a table, without first saving it as a file to disk and using readtable?

更多回答（1 个）

Amit Dhakite
Amit Dhakite 2023-2-14
Ran in:
Hi Lars Svensson,
As per my understanding, you are not able to extract the data from NIER Database, as the data present there is in .px format. When I was trying to extract that data mentioning .px format in the query, I was getting an array of dimension [22750 x 1 unit8], which doesn’t meet the requirements.
url = 'http://prognos.konj.se/PxWeb/api/v1/en/SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px';
query = '{"query": [],"response": {"format": "px"}}';
data = webwrite(url, query);
The data can be obtained in a struct using below code:
url = 'http://prognos.konj.se/PxWeb/api/v1/en/SenastePrognosen/f12_hushallensdisponiblainkomster/F1201.px';
% Mention the format as "json"
query = '{"query": [],"response": {"format": "json"}}';
data = webwrite(url, query);
t = data.data;
You can access the data and create a MATLAB table according to your requirements using that struct. An example for accessing the data is attached below:
Index = ["Current_prices_SEK_million";"Constant_prices_percentage_change";"Current_prices_SEK_million"];
% The values are present in the gap of 40 indices.
Year_1993 = [t(1).values; t(41).values; t(81).values];
Year_1994 = [t(2).values; t(42).values; t(82).values];
Year_1995 = [t(3).values; t(43).values; t(83).values];
RequiredTable = table(Index, Year_1993, Year_1994, Year_1995)
RequiredTable = 3×4 table
Index Year_1993 Year_1994 Year_1995 ___________________________________ ____________ ____________ ____________ "Current_prices_SEK_million" {'788990.0'} {'822728.0'} {'883842.0'} "Constant_prices_percentage_change" {'NA' } {'1.6' } {'4.3' } "Current_prices_SEK_million" {'646219.0'} {'672630.0'} {'705651.0'}
The table present on the database:
For more information, kindly go through the following documents:
  • How to create a MATLAB Table: Link
  • Using webwrite: Link

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