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<title>Quantile-normalize intensity measurements</title>

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<h1 class="title toc-ignore">Quantile-normalize intensity measurements</h1>
<h4 class="author"><em>Joyce Hsiao</em></h4>

</div>


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<p><strong>Last updated:</strong> 2017-12-11</p>
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<p><strong>Code version:</strong> a5ec074</p>
<hr />
<div id="introduction" class="section level2">
<h2>Introduction</h2>
<p>Previously when investigating measurement variation (GFP/RFP/FAPI), we learned that there’s significant variation between batches in the distributions of background-corrected pixel intensites. See <a href="../docs/images-qc-labels.html">here</a>.</p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Approach:</strong></p>
<p>In this document, I apply quantile normalization to intensity measurements on a per-channel basis. The approach is as follows</p>
<ol style="list-style-type: decimal">
<li><p>Construct a reference intensity. Estimate k-quantiles of reference intensities <span class="math inline">\(Q^{R,k}= \big( {q^{R,k}_{[1]}, \dots, q^{R,k}_{[n_k]}} \big)\)</span>.</p></li>
<li><p>For each plate <span class="math inline">\(i\)</span>, estimate <span class="math inline">\(l\)</span>-quantiles of intensities on a per-plate basis <span class="math inline">\(Q^{i,l}= \big( {q^{i,l}_{[1]}, \dots, q^{i,l}_{[n_l]}} \big)\)</span>.</p></li>
<li><p>For each plate <span class="math inline">\(i\)</span>, compare the intensity value <span class="math inline">\(F_{ij}\)</span> with the quantile values <span class="math inline">\(\big( {q^{i,l}_{[1]}, \dots, q^{i,l}_{[n_l]}} \big)\)</span> and assign image/well <span class="math inline">\(j\)</span> with the quantile that has the closest intensity value, say <span class="math inline">\(q^{i,l}_{[m]}\)</span> if <span class="math inline">\(m= argmin_{(1,\dots,n_l)} |F_{ij}- q^{i,l}_{[n_l]}|\)</span>. Then subsitute the intensity value with the <span class="math inline">\(m\)</span>-th quantile value in the reference intensity <span class="math inline">\(q^{R,k}_{[m]}\)</span>.</p></li>
</ol>
<p><span class="math inline">\(~\)</span></p>
<p>I tried two methods for constructing reference intensity vector, and the results are vastly different depends on the method that we choose.</p>
<p><em>Method 1</em>: Aggregate intensity values aross plates.</p>
<p><em>Method 2</em>: Take the average of <span class="math inline">\(n\)</span>-quantiles across plates.</p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Results:</strong></p>
<ol style="list-style-type: decimal">
<li><p>We chose 1/.005 quantiles for all three channels. See the document for our exploratory analysis of intensities from all three channels.</p></li>
<li><p>Method 1 versus Method 2: Because in Method 1, the distribution of Green/Red is more dense toward low and high-valued intensities, we see that the normalized values are closer toward the boundaries.</p></li>
<li><p>Method 2 of constructing the reference produces better results. We see that the relationship between Green/Red is preserved before versus after normalization.</p></li>
<li><p>In Method 2, after normalization, the range of intensities is the same between plates for each of the three channels (Green, Red, DAPI). As a result, many of the images/wells with low intensties decreased in intensity values.</p></li>
<li><p>Because of 4, the distances between samples in many plates increase rather than decrease. We were looking for decrease in the distances between samples, i.e., tighter clusters or smaller within-cluster distance…</p></li>
</ol>
<hr />
</div>
<div id="load-packages-and-data" class="section level2">
<h2>Load packages and data</h2>
<pre class="r"><code>ints &lt;- readRDS(file=&quot;/project2/gilad/joycehsiao/fucci-seq/data/intensity.rds&quot;)</code></pre>
<hr />
<p><span class="math inline">\(~\)</span></p>
</div>
<div id="densit-plots" class="section level2">
<h2>Densit plots</h2>
<p><span class="math inline">\(~\)</span></p>
<p>First, look at the distribution of all batches combined versus each batch.</p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-3-1.png" width="672" style="display: block; margin: auto;" /></p>
<hr />
<p><span class="math inline">\(~\)</span></p>
</div>
<div id="normalization" class="section level2">
<h2>Normalization</h2>
<p><span class="math inline">\(~\)</span></p>
<p>Code for one single sample</p>
<p><span class="math inline">\(~\)</span></p>
<pre class="r"><code>my_quantnorm &lt;- function(reference, sample, span=.01) {
  # quantiles for intensities all samples across plates
  quants_reference &lt;- quantile(reference, probs=seq(0,1,span))
  # intensities for a given plate
  # quantiles for intensities at each plate
  quants_sample &lt;- quantile(sample, probs=seq(0,1,span))
  # empty vector for normalized values
  sample_normed &lt;- vector(&quot;numeric&quot;, length=length(sample))
  
  for (index in 1:length(sample)) {
    # for each sample, find the closest sample quantile
    sample_order &lt;- names(which.min(abs(sample[index]-quants_sample)))
    # # get the reference intensity value of the closet quantile
    ref_order_value &lt;- reference[which(names(quants_reference)==sample_order)] 
    # assign the reference intensity value to the sample
    sample_normed[index] &lt;- ref_order_value 
  }
  return(sample_normed)
}</code></pre>
<p><span class="math inline">\(~\)</span></p>
<div id="choosing-quantile-interval" class="section level3">
<h3>Choosing quantile interval</h3>
<p><span class="math inline">\(~\)</span></p>
<p><strong>RFP</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-5-1.png" width="672" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>GFP</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-6-1.png" width="672" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-7-1.png" width="672" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
</div>
<div id="method-1" class="section level3">
<h3>Method 1</h3>
<p>Method 1 constructs a vector of refernece intensity by aggregating all image intensity values across plates.</p>
<p><span class="math inline">\(~\)</span></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Distribution of the reference</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-9-1.png" width="480" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>After normalization</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-10-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green versus Red intensties by plate, labeled by DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-11-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green versus Red intensties by individual, labeled by DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-12-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-13-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Red</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-14-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-15-1.png" width="1152" style="display: block; margin: auto;" /></p>
<hr />
<p><span class="math inline">\(~\)</span></p>
</div>
<div id="method-2" class="section level3">
<h3>Method 2</h3>
<p><span class="math inline">\(~\)</span></p>
<p>Reference intensity vector: average of quantile values across plates.</p>
<p><span class="math inline">\(~\)</span></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>After normalization</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-17-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green versus Red intensties by plate, labeled by DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-18-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green versus Red intensties by individual, labeled by DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-19-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Green</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-20-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>Red</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-21-1.png" width="1152" style="display: block; margin: auto;" /></p>
<p><span class="math inline">\(~\)</span></p>
<p><strong>DAPI</strong></p>
<p><span class="math inline">\(~\)</span></p>
<p><img src="figure/images-normalize-quantile.Rmd/unnamed-chunk-22-1.png" width="1152" style="display: block; margin: auto;" /></p>
<hr />
</div>
</div>
<div id="session-information" class="section level2">
<h2>Session information</h2>
<pre><code>R version 3.4.1 (2017-06-30)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Scientific Linux 7.2 (Nitrogen)

Matrix products: default
BLAS: /home/joycehsiao/miniconda3/envs/fucci-seq/lib/R/lib/libRblas.so
LAPACK: /home/joycehsiao/miniconda3/envs/fucci-seq/lib/R/lib/libRlapack.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] Biobase_2.38.0      BiocGenerics_0.24.0 RColorBrewer_1.1-2 
[4] wesanderson_0.3.2   cowplot_0.8.0       ggplot2_2.2.1      
[7] dplyr_0.7.0         data.table_1.10.4  

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.14     knitr_1.16       magrittr_1.5     munsell_0.4.3   
 [5] colorspace_1.3-2 R6_2.2.0         rlang_0.1.2      stringr_1.2.0   
 [9] plyr_1.8.4       tools_3.4.1      grid_3.4.1       gtable_0.2.0    
[13] git2r_0.19.0     htmltools_0.3.6  lazyeval_0.2.0   yaml_2.1.14     
[17] rprojroot_1.2    digest_0.6.12    assertthat_0.1   tibble_1.3.3    
[21] glue_1.1.1       evaluate_0.10.1  rmarkdown_1.6    labeling_0.3    
[25] stringi_1.1.2    compiler_3.4.1   scales_0.4.1     backports_1.0.5 </code></pre>
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