在MATLAB中按值对JSON进行排序

Question

我想在JSON文件中按"；createdAt"；并在绘图函数中使用这些值。正如你所看到的，这列存储日期值，所以我已经转换了它。我已经应用了排序函数，但当我看到数据的输出时，它似乎不适用排序。

data = loadjson('C:/data/default.json');
count_data = sum(cellfun(@(x) numel(x),data.Location)); %returns 21
for i=1:count_data
createdAt= cellfun( @(cellElem) cellElem.createdAt, data.Location ,'UniformOutput',false);
createdAtDate= datetime(createdAt(i),'InputFormat','dd-MM-yyyy HH:mm:ss','Format', 'dd-MM-yyyy n HH:mm:ss');
[~,X] = sort(createdAtDate,'descend');
out=data(X);
end
for i=1:count_data
x = cellfun( @(cellElem) cellElem.createdAt, out.Location,'UniformOutput',false);
disp(x);
end

我的JSON文件：

"Location": [
{
"id": "0b5965e5-c509-4522-a525-8ef5a49dadaf",
"measureId": "5a6e9b79-dbb1-4482-acc1-d538f68ef01f",
"locationX": 0.9039769252518151,
"locationY": 0.2640594070404616,
"createdAt": "06-01-2021 19:38:44"
},
{
"id": "18714a2f-a8b3-4dc6-8a5b-114497fa9671",
"measureId": "671f52bc-a066-494a-9dce-6e9ccfac6c1d",
"locationX": 1.5592001730078755,
"locationY": 0.5207689756815629,
"createdAt": "06-01-2021 19:35:24"
},

提前谢谢。

Answer 1

您需要提取所有需要的数据，然后对进行排序

即

x = cellfun( @(cellElem) cellElem.locationX, data.Location );
y = cellfun( @(cellElem) cellElem.locationY, data.Location );
% Get date strings
d = cellfun( @(cellElem) cellElem.createdAt, data.Location, 'UniformOutput', false)
% Convert to datetime
d = datetime( d, 'InputFormat', 'dd-MM-yyyy HH:mm:ss' );
% Get the sort order
[~,idx] = sort( d );
% Sort other arrays
x = x(idx);
y = y(idx);

另一种选择是使用表

x = cellfun( @(cellElem) cellElem.locationX, data.Location );
y = cellfun( @(cellElem) cellElem.locationY, data.Location );
% Get dates
d = cellfun( @(cellElem) cellElem.createdAt, data.Location, 'UniformOutput', false)
d = datetime( d, 'InputFormat', 'dd-MM-yyyy HH:mm:ss' );
% Create table
t = table( x(:), y(:), d(:), 'VariableNames', {'locationX','locationY','createdAt'} );
% Sortrows
t = sortrows( t, 'createdAt' );

这里必须使用表而不是矩阵(尽管sortrows可以接受任何一种(，因为列之间的数据类型是混合的。