0

我正在使用 API 来获取火车的真实数据时间，并试图获得与用户输入时间最接近的火车时间，然后显示该火车时间，接下来的 4 个火车正在运行。我正在阅读信息，代码完成了它应该做的事情，但是当我查看数组时，它是 7 个单元格中的一堆 [] 括号，而不是计算出来的数字。有什么建议么？代码如下与 API

测试值：requestStationSelected = 'University%20City' 和 requestEndStation = 'Roslyn'

%this is the API link for the live data from Septa this will get 30
%results and see which time is closer to the user entered time
requestInfoSeptaLive = ['http://www3.septa.org/hackathon/NextToArrive/' requestStationSelected '/' requestEndStation '/30'];

%Again tries to get the information and if there is a failure it will give
%a probable cause and terminate the program
try
    getInfoSeptaLive = urlread(requestInfoSeptaLive);
catch
    if getInfoSeptaLive ~= '[]'
        disp...
            ('Either the arrival/depart stations dont quite match up or theres a server error. Try again.');
        return;
    else
        disp('Unable to fetch the information from Septa, please try again')
        return;
    end
end
%parses the information returned from the Live API
dataReturnedFromLiveAPI = parse_json(getInfoSeptaLive);
dataReturnedFromLiveAPI = dataReturnedFromLiveAPI{1};

%gets the size of the API in case there are no trains running
sizeOfDataNoTrains = size(dataReturnedFromLiveAPI, 1);
sizeOfData = size(dataReturnedFromLiveAPI, 2);

counter = 0;

for i = 1:sizeOfData
    scanForClosestTime = dataReturnedFromLiveAPI{1,i}.orig_departure_time;

    trainTimeGivenH = sscanf(scanForClosestTime, '%i');
    findColonTrain = strfind(scanForClosestTime, ':');
    trainTimeGivenMStr = scanForClosestTime(findColonTrain+1:4);
    trainTimeGivenM = int32(str2num(trainTimeGivenMStr));
    trainDepartTimeM = (trainTimeGivenH(1,1) * 60) + (trainTimeGivenM);

    differenceBetweenTimes = trainDepartTimeM - userEnteredMins;
    if trainDepartTimeM < userEnteredMins
        differenceBetweenTimes = userEnteredMins - trainDepartTimeM;
    end

    stopAtEndOfData = sizeOfData;
    goodTimeFrame = 60;
    closestTime = cell(1, stopAtEndOfData);
    storeTheDifference = cell(1, stopAtEndOfData);

    if(differenceBetweenTimes < 60)
        if (counter < 5)
            closestTime{i} = scanForClosestTime;
            storeTheDifference{i} = differenceBetweenTimes;
            counter = counter + 1;
        end
    end
end
4

1 回答 1

1

您在for循环内分配单元格数组：

for i = 1:sizeOfData
    ...
        closestTime = cell(1, stopAtEndOfData);
        storeTheDifference = cell(1, stopAtEndOfData);
    ...
end

这意味着您{[],[],[],[],[]...}在循环的每次迭代中都将它们都变成一个数组 - 所以除非最后一次迭代中有一个有效的“最近时间”，否则您的单元格数组将都是空数组 - 如果是这样，除了最后一个元素仍然是 []。

要解决此问题，请将这两行移到循环开始之前。for

第二个问题似乎是存储结果的数组的索引。如果您只想要五个结果，我假设您想将它们存储在数组的元素 1 - 5 中，而不是“任意”位置。我会将代码更改为

    if (counter < 5)
        counter = counter + 1;
        closestTime{counter} = scanForClosestTime;
        storeTheDifference{counter} = differenceBetweenTimes;
    end

但也许我误解了你想如何处理它？

与您的问题无关，您可能想看看该行

trainTimeGivenMStr = scanForClosestTime(findColonTrain+1:4);

这很可能不是您打算做的 - 查看响应示例，我找到了 string "orig_departure_time":"11:57PM"。我希望这样findColonTrain == 3，所以上面的行变成

trainTimeGivenMStr = scanForClosestTime(4:4);

  • 只是一个字符。也许你的意思是

    trainTimeGivenMStr = scanForClosestTime(findColonTrain+(1:4));

这将变成

trainTimeGivenMStr = scanForClosestTime(4:7);

以便

trainTimeGivenMStr = '57PM';

我希望这三件事可以帮助您完成所有工作！

编辑：今天早上有机会运行您的代码 - 发现了许多其他问题。我在下面包含一个带注释的“工作”代码：最大的问题很可能是您没有在代码中处理 AM/PM。请注意，我使用了不同的 json 解析器——这改变了几行。我相信您可以将其重新组合在一起以按照您想要的方式工作。这在所有单元格中返回了有效数据。

dataReturnedFromLiveAPI = loadjson(getInfoSeptaLive);
% next line not needed - loadjson returns struct array, not cell array
%dataReturnedFromLiveAPI = dataReturnedFromLiveAPI{1};

%gets the size of the API in case there are no trains running
sizeOfDataNoTrains = size(dataReturnedFromLiveAPI, 1);
sizeOfData = size(dataReturnedFromLiveAPI, 2);

counter = 0;
stopAtEndOfData = sizeOfData;
closestTime = cell(1, stopAtEndOfData);
storeTheDifference = cell(1, stopAtEndOfData);
userEnteredMins = 12*60+30; % looking for a train around 12:30 pm

for ii = 1:sizeOfData
    scanForClosestTime = dataReturnedFromLiveAPI(ii).orig_departure_time;

    trainTimeGivenH = sscanf(scanForClosestTime, '%i');
    % since we'll be considering AM/PM, have to set 12 = 0:
    if (trainTimeGivenH == 12), trainTimeGivenH = 0; end
    findColonTrain = strfind(scanForClosestTime, ':');
    % change next line to get minutes plus AM/PM:
    trainTimeGivenMStr = scanForClosestTime(findColonTrain+(1:4));
    % look at just minutes:
    trainTimeGivenM = int32(str2num(trainTimeGivenMStr(1:2)));
    % adjust for AM/PM:
    if(trainTimeGivenMStr(3:4)=='PM'), trainTimeGivenH = trainTimeGivenH+12; end;
    % compute time in minutes:
    trainDepartTimeM = (trainTimeGivenH * 60) + (trainTimeGivenM);

    differenceBetweenTimes = trainDepartTimeM - userEnteredMins;
    if trainDepartTimeM < userEnteredMins
        differenceBetweenTimes = userEnteredMins - trainDepartTimeM;
    end
    % added a couple of lines to see what is happening:
    fprintf(1, 'train %d: depart %s - in minutes this is %d vs user entered %d\n', ...
        ii, scanForClosestTime, trainDepartTimeM, userEnteredMins);

    goodTimeFrame = 60;

    if(differenceBetweenTimes < 600)
        if (counter < 10)
            counter = counter + 1;
            closestTime{counter} = scanForClosestTime;
            storeTheDifference{counter} = differenceBetweenTimes;
        end
    end
end
于 2013-03-09T03:55:11.487 回答