How to extract data from variable

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Manfred
Manfred 2023-4-26
评论： Christopher Stapels 2023-4-26
Hi,
In my Mathwork Analysis module, the result of
disp(data);
shown in the command window is
{"temperature"=>10.4, "windspeed"=>12.3, "winddirection"=>255.0, "weathercode"=>3, "is_day"=>1, "time"=>"2023-04-26T14:00"}
How can I extract a single value, for example "windspeed"?
  1 个评论
Christopher Stapels
Christopher Stapels 2023-4-26
Can you show us more code? For example, how do you get the values into the variable 'data'? It looks like it might be a struct. If so, you can access the specific memebrs using dot notation
data.windspeed
for example
or
disp(data.windspeed)

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回答（2 个）

albara
albara 2023-4-26
You can extract the value associated with the "windspeed" key using MATLAB's built-in jsondecode function. Here's an example code snippet:
% Assume your JSON data is stored in a string variable named 'data'
data = '{"temperature":10.4, "windspeed":12.3, "winddirection":255.0, "weathercode":3, "is_day":1, "time":"2023-04-26T14:00"}';
% Decode the JSON data using jsondecode
json_data = jsondecode(data);
% Extract the windspeed value
windspeed = json_data.windspeed;
% Print the windspeed value to the command window
disp(windspeed);
Make sure that the JSON data is correctly formatted and that the keys and values are separated by : symbols.
Important: There may be some mistakes in this answer Experts can tell if there are any mistakes
  2 个评论
Manfred
Manfred 2023-4-26
I get the data by an webread command. There are "=>" charcters instead of ":" in the string. If i exchange them, it work like you explained.
Is there an webread option that might solve this problem?
Manfred
Manfred 2023-4-26
编辑：Manfred 2023-4-26
I solved the problem myself by the strrep function
data = jsondecode(strrep(data,'=>',':'));
Thank you for your helpful response.

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Image Analyst
Image Analyst 2023-4-26
What does this show:
whos data
I need to know what kind of variable it is. It doesn't look like a cell array. It looks more like a dictionary.
Does
windSpeed = data.windspeed
work?
  5 个评论
显示 3更早的评论
Image Analyst
Image Analyst 2023-4-26
I'd look into correcting why it put => in there instead of : in the first place. Did you create the strings, or is it something someone else made up and posted online and you need to read and parse that data?
Manfred
Manfred 2023-4-26
编辑：Manfred 2023-4-26
I solved the problem myself by the strrep function
data = jsondecode(strrep(data,'=>',':'));
Thank you for your helpful response.

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