我在mathematica中有以下内容并希望在matlab中使用它。我试过但我有错误而且无法修复它们。我还没有得到matlab哲学! 所以,
intMC = {}; sigmat = {};
Do[np1 = np + i*100;
xpoints = Table[RandomReal[], {z1, 1, np1}];
a1t = Table[f[xpoints[[i2]]], {i2, 1, np1}];
a12 = StandardDeviation[a1t]/Sqrt[Length[a1t]];
AppendTo[intMC, {np1, Mean[a1t], a12}];
AppendTo[sigmat, {np1, a12}],
{i, 1, ntr}];
我这样做了:
fx=@ (x) exp(-x.^2);
intmc=zeros();
sigmat=zeros();
for i=1:ntr
np1=np+i*100;
xpoints=randn(1,np1);
for k=1:np1
a1t=fx(xpoints(k))
end %--> until here it prints the results,but in the
%end it gives
% me a message " Attempted to access xpoints(2,:);
%index out of bounds because size(xpoints)=[1,200]
%and stops executing.
%a1t=fx(xpoints(k,:)) % -->I tried this instead of the above but
%a1t=bsxfun(@plus,k,1:ntr) % it doesn't work
a12=std(a1t)/sqrt(length(a1t))
intmc=intmc([np1 mean(a1t) a12],:) %--> i can't handle these 3 and
sigmat=sigmat([np1 a12 ],:) %as i said it stopped executing
end
答案 0 :(得分:2)
为了将标量附加到Matlab数组,您可以调用array(end+1) = value
或array = [array;value]
(如果需要1-by-n数组,则用逗号替换分号)。后者也适用于附加数组;要使用前者附加数组,您可以调用array(end+1:end:size(newArray,1),:) = newArray
,以防您想要沿着第一维进行连接。
然而,在Matlab中追加超过100次迭代的循环是一个坏主意,因为它很慢。你最好先预先分配数组 - 甚至更好,矢量化计算,这样你就不需要循环了。
如果我理解正确,您需要从正态分布的越来越多的样本中计算平均值和SEM。以下是循环执行此操作的方法:
intmc = zeros(ntr,3); %# stores, on each row, np1, mean, SEM
sigmat = zeros(ntr,2); %# stores, on each row, np1 and SEM
for i=1:ntr
%# draw np+100*i normally distributed random values
np1 = np+i*100;
xpoints = randn(np1,1);
%# if you want to use uniform random values (as in randomreal), use rand
%# Also, you can apply f(x) directly on the array xpoints
%# caculate mean, sem
m = mean(xpoints);
sem = std(xpoints)/sqrt(np1);
%# store
intmc(i,:) = [np1, m, sem];
sigmat(i,:) = [np1,sem];
end %# loop over i