Find previous time conditions were met, save it as new marix

Question

SBinary 2018-11-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/430094-find-previous-time-conditions-were-met-save-it-as-new-marix

评论： SBinary 2018-11-20

I am working with ecology data. Presence/absence data (Y) has been collected for 100 sites (X) over 10 years (Z), on a rotational basis (30 per year). To illusterate: site X(1) could, for example, be surveyed year [1,4,7,10], site X(2) surveyed year [2,3,4,8], site X(3) surveyed [3,5].

To better explain observed presence/absence (Y) in a given year z I would like to use presence/absence data (Y) from the previous time a given site x was surveyed.

I am at a loss where to begin. Any advice/pointers to get me started would be much appreciated.

Many thanks

J

4 个评论
显示 2更早的评论隐藏 2更早的评论

Adam Danz 2018-11-16

在 MATLAB Online 中打开

To get all rows numbers where site number 'j' was surveyed, use find(). For example for site number 9:

rowNums = find(X == 9);

rowNums will be a vector of row numbers such as [ 3; 22; 31; 48 ...]; If you're looking at row number 22, the previous time site number 9 was surveyed is in row number 3.

SBinary 2018-11-19

Thank you very much, Adam! Question solved. Much appreciated!

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Peter Perkins 2018-11-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/430094-find-previous-time-conditions-were-met-save-it-as-new-marix#answer_347853

在 MATLAB Online 中打开

Joel, it's hard to tell, but it seems very likely that you'd benefit from putting your data in a timetable. "30 per year" sounds like you have timestamps to a resolution smaller than whole years. Timetables let you select data by time.

You could also convert your species and sites to categorical. You might find it more palatable to write

  mydata(mydata.Species1=='Cryptobranchus alleganiensis' & mydata.Site=='Oneonta',:)

to select data.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

SBinary 2018-11-20

Thanks, Peter. Very useful advice! I still have some way to go from writing code that works, to code that is also elegant and efficient. The reason for working in the data format(s) I was in particular case was to conform to the standard used in the ecological model framework/library I am trying to adapt to my needs. I will definitely try to implement your ideas, though, as they would indeed be beneficial.

请先登录，再进行评论。