[R] dependent nested for loops in R

[David Winsemius]

Or perhaps you wanted:

W <- z
W[z>4|z<2] <- 0

Sent from my iPhone

> On Feb 1, 2021, at 9:41 PM, David Winsemius <dwinsemius using comcast.net> wrote:
> 
> Just drop the “+” if you want logical. 
> 
> Sent from my iPhone
> 
>>> On Feb 1, 2021, at 9:36 PM, Shaami <nzshaam using gmail.com> wrote:
>>> 
>> 
>> Hi Prof. David
>> 
>> Thank you. I will always follow your advice. The suggested code worked. It gives either 1 or 0 depending on the condition to be true. I want index of z for which the condition is true (instead of 1) else zero. Could you please suggest? 
>> 
>> Thank you
>> 
>> Shaami
>> 
>>> On Tue, Feb 2, 2021 at 10:16 AM David Winsemius <dwinsemius using comcast.net> wrote:
>>> Cc’ed the list as should always be your practice. 
>>> 
>>> Here’s one way (untested):
>>> 
>>> W <- +(z>4| z<2) # assume z is of length 20
>>> 
>>> — 
>>> David
>>> 
>>> Sent from my iPhone
>>> 
>>>>> On Feb 1, 2021, at 7:08 PM, Shaami <nzshaam using gmail.com> wrote:
>>>>> 
>>>> 
>>>> Hi Prof. David
>>>> 
>>>> In the following state
>>>> 
>>>> W = (1:2000)[z >4|z<2)
>>>> 
>>>> Could you please guide how  I can assign zero if condition is not satisfied?
>>>> 
>>>> Best Regards 
>>>> 
>>>> Shaami
>>>> 
>>>>> On Mon, 1 Feb 2021, 11:01 am David Winsemius, <dwinsemius using comcast.net> wrote:
>>>>> 
>>>>> On 1/31/21 1:26 PM, Berry, Charles wrote:
>>>>> >
>>>>> >> On Jan 30, 2021, at 9:32 PM, Shaami <nzshaam using gmail.com> wrote:
>>>>> >>
>>>>> >> Hi
>>>>> >> I have made the sample code again. Could you please guide how to use
>>>>> >> vectorization for variables whose next value depends on the previous one?
>>>>> >>
>>>>> 
>>>>> I agree with Charles that I suspect your results are not what you 
>>>>> expect. You should try using cat or print to output intermediate results 
>>>>> to the console. I would suggest you limit your examination to a more 
>>>>> manageable length, say the first 10 results while you are working out 
>>>>> your logic. After you have the logic debugged, you can move on to long 
>>>>> sequences.
>>>>> 
>>>>> 
>>>>> This is my suggestion for a more compact solution (at least for the 
>>>>> inner loop calculation):
>>>>> 
>>>>> set.seed(123)
>>>>> 
>>>>> x <- rnorm(2000)
>>>>> 
>>>>> z <- Reduce( function(x,y) { sum(y+5*x) }, x, accumulate=TRUE)
>>>>> 
>>>>> w<- numeric(2000)
>>>>> 
>>>>> w <-  (1:2000)[ z >4 | z < 1 ]  # In your version the w values get 
>>>>> overwritten and end up all being 2000
>>>>> 
>>>>> 
>>>>> I would also advise making a natural language statement of the problem 
>>>>> and goals. I'm thinking that you may be missing certain aspects of the 
>>>>> underying problem.
>>>>> 
>>>>> -- 
>>>>> 
>>>>> David.
>>>>> 
>>>>> >
>>>>> > Glad to help.
>>>>> >
>>>>> > First, it could help you to trace your code.  I suspect that the results are not at all what you want and tracing would help you see that.
>>>>> >
>>>>> > I suggest running this revision and printing out x, z, and w.
>>>>> >
>>>>> > #+begin_src R
>>>>> >    w = NULL
>>>>> >    for(j in 1:2)
>>>>> >    {
>>>>> >      z = NULL
>>>>> >      x = rnorm(10)
>>>>> >      z[1] = x[1]
>>>>> >      for(i in 2:10)
>>>>> >      {
>>>>> >        z[i] = x[i]+5*z[i-1]
>>>>> >        if(z[i]>4 | z[i]<1) {
>>>>> >       w[j]=i
>>>>> >        } else {
>>>>> >       w[j] = 0
>>>>> >        }
>>>>> >      }
>>>>> >    }
>>>>> > #+end_src
>>>>> >
>>>>> >
>>>>> > You should be able to see that the value of w can easily be obtained outside of the `i' loop.
>>>>> >

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