How to delete or ignore the rows with duplicate values in time

Question

Simona Blaskova 2023-6-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1986339-how-to-delete-or-ignore-the-rows-with-duplicate-values-in-time

评论： Simona Blaskova 2023-6-23

I have a 26400x2 table with time and numbers representing satellite IDs for every second (as in the picture, the file is too large to upload). I need to get the number of satellites in time (which I want to plot later). This should simply be the height of each vector containing 1 second. However, there are some duplicate sat IDs in each second, and I don't know how to remove them. I tried the following:

t1 = raw.UTCTime(1);
t2 = raw.UTCTime(end);
t = (t1:seconds(1):t2)';
num_sats_gps = zeros(length(t),1);
for i = 1:length(t)
    idx = gps.UTCTime == t(i);
    uniq = unique(gps.Svid(idx));
    num_sats_gps(i,1) = height(uniq);
end

but it doesn't work like it's supposed to, the result gives me vector with 0 values. Is there any other approach to this? Any answer would be highly appreciated!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Yash 2023-6-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1986339-how-to-delete-or-ignore-the-rows-with-duplicate-values-in-time#answer_1260114

There might be an issue with how you're indexing the table or filtering duplicates, other than that, your code seems right to me.

As an alternative, you can use the 'splitapply' function. Take the help of the below mentioned code.

% Assuming your table is named 'raw' with columns 'UTCTime' and 'Svid'

t1 = raw.UTCTime(1);

t2 = raw.UTCTime(end);

t = (t1:seconds(1):t2)';

%Storing the resulting count in num_sats_gps

num_sats_gps = splitapply(@(x) numel(unique(x)), raw.Svid, discretize(raw.UTCTime, t));

%Using 'discretize' function to divide the time range into one-second intervals

The splitapply function applies the anonymous function @(x) numel(unique(x)) to each group of satellite IDs (x) associated with a specific time interval. It counts the number of unique satellite IDs in each group.

Hope this helps.