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(This article was first published on <strong><a href="http://r-exercises.com/2016/12/08/matrix-vol-2-exercises/"> R-exercises</a></strong>, and kindly contributed to <a rel="nofollow" href="https://www.r-bloggers.com/">R-bloggers)</a> </div>
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<p>[For this exercise, first write down your answer, without using R. Then, check your answer using R.]</p>
<p>Answers to the exercises are available <a target="_blank" rel="nofollow" href="http://r-exercises.com/2016/12/08/matrix-vol-2-solutions/">here</a>.</p>
<p><strong>Exercise 1</strong></p>
<p>If<br>
<code>M=matrix(c(1:10),nrow=5,ncol=2,<br>
dimnames=list(c('a','b','c','d','e'),c('A','B')))</code></p>
<p>What is the value of: <code>M</code></p>
<p><strong>Exercise 2</strong></p>
<p>Consider the matrix <code>M</code>,<br>
What is the value of:<br>
<code>M[1,]</code><br>
<code>M[,1]</code><br>
<code>M[3,2]</code><br>
<code>M['e','A']</code></p>
<p><strong>Exercise 3</strong></p>
<p>Consider the matrix <code>N</code><br>
<code>N=matrix(c(1:9),nrow=3,ncol=3,<br>
dimnames=list(c('a','b','c'),c('A','B','C')))<br>
</code><br>
What is the value of: <code>diag(N)</code></p>
<p><strong>Exercise 4</strong></p>
<p>What is the value of: <code>diag(4,3,3)</code><br>
Is matrix ?</p>
<p><strong>Exercise 5</strong></p>
<p>If <code>M=matrix(c(1:9),3,3,byrow=T,<br>
dimnames=list(c('a','b','c'),c('d','e','f')))</code><br>
What is the value of:<br>
<code>rownames(M)</code><br>
<code>colnames(M)</code></p>
<p><strong>Exercise 6</strong></p>
<p>What is the value of:<br>
<code>upper.tri(M)</code><br>
<code>lower.tri(M)</code><br>
<code>lower.tri(M,diag=T)</code></p>
<p><strong>Exercise 7</strong></p>
<p>Consider two matrix,<br>
<code>M,N<br>
</code><br>
<code>M=matrix(c(1:9),3,3,byrow=T)</code><br>
<code>N=matrix(c(1:9),3,3)<br>
</code><br>
What is the value of:</p>
<p><code>M*N<br>
</code></p>
<p><strong>Exercise 8</strong></p>
<p>Consider two matrix,<br>
<code>M,N<br>
</code><br>
<code>M=matrix(c(1:9),3,3,byrow=T)</code><br>
<code>N=matrix(c(1:9),3,3)<br>
</code><br>
What is the value of:</p>
<p><code>M%*%N<br>
</code></p>
<p><strong>Exercise 9</strong></p>
<p>Consider two matrix,<br>
<code>M,N<br>
</code><br>
<code>M=matrix(c(1:9),3,3,byrow=T)</code><br>
<code>N=matrix(c(1:9),3,3)<br>
</code></p>
<p>What is the value of:</p>
<p><code>(M+N)^2</code></p>
<p><strong>Exercise 10</strong><br>
Consider two matrix,<br>
<code>M,N<br>
</code><br>
<code>M=matrix(c(1:9),3,3,byrow=T)</code><br>
<code>N=matrix(c(1:9),3,3)<br>
</code></p>
<p>What is the value of:</p>
<p><code>M/N</code></p>
<p><strong>Want to practice matrices a bit more? We have more exercise sets on this topic <a target="_blank" rel="nofollow" href="http://r-exercises.com/tag/matrix">here</a>.</strong></p>
<p>
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