Homework 1

  • Due Sep 17, 2021 by 11:59pm
  • Points 100
  • Submitting a file upload

Homework Project 1

Problem 1.1 (Long-to-Wide Data format translation):

We demonstrated the wide-to-long conversion in lecture. Now, let’s explore long-to-wide. Load in the SOCR Pediatric Normal and Schizophrenia Neuroimaging Study Dataset Links to an external site.. It's in a wide format where 56 different regional cortical and subcortical volumes contain information we want to represent in long format. Convert the original from wide-to-long and then back to wide format.

Problem 1.2 (Data stratification):

Use the same Schizophrenia Neuroimaging Study Dataset Links to an external site. and complete the following data-manipulation steps in R:

  • Extract the first 10 subjects
  • Find the cases for which L_caudate < 160.
  • Sort the subjects based on L_caudate values in descending and ascending order.
  • Generate frequency and probability tables for Age, FS_IQ, and Sex.
  • Compute the mean Age and the correlation between Age and FS_IQ.
  • Plot Histogram and density of R_fusiform_gyrus, and draw scatterplot L_fusiform_gyrus and L_insular_cortex.
Problem 1.3 (Simulation)

Generate 1,000 standard normal variables and another 1,200 student t distributed random variables with df=20. Generate a quantile-quantile (Q-Q) probability plot of the two samples. Then, compare it with qqnorm() or plot_ly()  of student t simulation and interpret the findings.

 

Problem 1.4 (Define an R median function)

Define a new function  myMedian() that computes a sample median and compare your function against the standard R  median() function using the simulation data you generate in the last question (1.3). Did you cover all possible situations for the input data?

1631937599 09/17/2021 11:59pm

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Total Points: 100 out of 100