Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>All standard variants of t-test use sample variances in their formulas, and you cannot compute that from one observation as you are dividing with n-1, where n is sample size.</p> <p>This would probably be the easiest modification, although I cannot test it as you did not provide sample data (you could <code>dput</code> your data to your question):</p> <pre><code> t&lt;- lapply(1:length(x), function(i){ if(length(x[[i]][[2]])&gt;1){ t.test(dat$Value,x[[i]][[2]]) } else "Only one observation in subset" #or NA or something else }) </code></pre> <p>Another option would be to modify the indices which are used in <code>lapply</code>:</p> <pre><code>ind&lt;-which(sapply(x,function(i) length(i[[2]])&gt;1)) t&lt;- lapply(ind, function(i) t.test(dat$Value,x[[i]][[2]])) </code></pre> <p>Here's an example of the first case with artificial data:</p> <pre><code>x&lt;-list(a=cbind(1:5,rnorm(5)),b=cbind(1,rnorm(1)),c=cbind(1:3,rnorm(3))) y&lt;-rnorm(20) t&lt;- lapply(1:length(x), function(i){ if(length(x[[i]][,2])&gt;1){ #note the indexing x[[i]][,2] t.test(y,x[[i]][,2]) } else "Only one observation in subset" }) t [[1]] Welch Two Sample t-test data: y and x[[i]][, 2] t = -0.4695, df = 16.019, p-value = 0.645 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: -1.2143180 0.7739393 sample estimates: mean of x mean of y 0.1863028 0.4064921 [[2]] [1] "Only one observation in subset" [[3]] Welch Two Sample t-test data: y and x[[i]][, 2] t = -0.6213, df = 3.081, p-value = 0.5774 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: -3.013287 2.016666 sample estimates: mean of x mean of y 0.1863028 0.6846135 Welch Two Sample t-test data: y and x[[i]][, 2] t = 5.2969, df = 10.261, p-value = 0.0003202 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: 3.068071 7.496963 sample estimates: mean of x mean of y 5.5000000 0.2174829 </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POError using t.test() in R - not enough 'y' observations
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USJouni Helske
    1. USJouni Helske
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POError using t.test() in R - not enough 'y' observations
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI edited my question and added some data..... I tried you have given me but I get errors like Error: unexpected '{' in "t<- lapply(1:length(x), function(i){if(length(x[[i]][[2]]>1){"
      singulars
      1. PO
      1. USFlay Auchter
    2. COOops, the code was missing one parenthesis, I corrected the code, should work now.
      singulars
      1. PO
      1. USJouni Helske
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload