NaN when calculating average

4 次查看（过去 30 天）
Pankaj
Pankaj 2012-1-22
I read data from a .xls file using xlsread. There are some 3000 rows with price data, all in number format in excel. I further try to calculate the average of previous 10 days for every day using mean2(prices(i-10,1):prices(i,1)). I do this for last 2990 rows. surprisingly a lot of these throw NaN. I have also run a check "isnan" on each element in prices and none of them tests positive. also stumbled on something:
isnumeric(NaN)
ans =
1
how is this working??

请先登录，再回答此问题。

采纳的回答

David Young
David Young 2012-1-22
Although a NaN is not a number, it is of class double, and so it is numeric. If a NaN was not numeric, it could not be held in a matrix with other numbers.
Your problem is that prices(i-10,1):prices(i,1) may be empty, so mean2 returns NaN. In fact, that expression doesn't look likely to be correct. I suspect you intended to use mean2(prices(i-10:i, 1)).

更多回答（2 个）

Andrew Newell
Andrew Newell 2012-1-22
You could use nanmean to ignore the NaN's while calculating means:
prices = rand(20,20);
n = size(prices,1); m = size(prices,2); window=10;
runningMean = zeros(n-window,m);
for ii=1:n-window
runningMean(ii,:) = nanmean(runningMean(ii:ii+window-1,:));
end
Note that I am interpreting your statement of "previous 10 days" as the ten days before the current day. Your version is actually averaging 11 days.
  6 个评论
显示 4更早的评论
Atakan
Atakan 2012-1-22
This is my code:
function [randnormal]=atakan(a,b,m)
randnormal=[];
count=1;
while (count<=m)
R = normrnd(a,b);
u1=unifrnd(0,1);
u2=unifrnd(0,1);
y=tan(pi*(u1-1/2));
if (u2<=((sqrt(exp(1))/2)*(1+y^2)*(exp(1)^(-y^2/2))))
randnormal=[R;y];
end
count=count+1;
end
Pankaj
Pankaj 2012-1-23
Thanks Andrew - good solution - it helps!

请先登录，再进行评论。

Atakan
Atakan 2012-1-22
Hi; I want to ask a question to the main page. But it gives an error such that "we are sorry but something went wrong". What can I do?
  3 个评论
显示 1更早的评论
Atakan
Atakan 2012-1-22
I have tried many many times. But there is still a problem. If I send the question to you, can you ask the question for me? Because this is very important for me. thanks...
Jan
Jan 2012-1-22
Dear Atakan: The servers have severe problems currently.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Logical 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by